diff --git a/src/alexa.zig b/src/alexa.zig
new file mode 100644
index 0000000..b69a5f2
--- /dev/null
+++ b/src/alexa.zig
@@ -0,0 +1,175 @@
+//! Alexa-specific utilities: context parsing and Settings API.
+
+const std = @import("std");
+const json = std.json;
+const http = std.http;
+const Allocator = std.mem.Allocator;
+const homeassistant = @import("homeassistant.zig");
+
+const log = std.log.scoped(.alexa);
+
+/// Context extracted from Alexa request
+pub const Context = struct {
+    api_endpoint: []const u8,
+    api_access_token: []const u8,
+    device_id: []const u8,
+};
+
+/// Parse Alexa context from request JSON.
+/// Returns null if context is missing or malformed.
+pub fn parseContext(json_value: json.Value) ?Context {
+    const obj = switch (json_value) {
+        .object => |o| o,
+        else => return null,
+    };
+
+    const context_obj = switch (obj.get("context") orelse return null) {
+        .object => |o| o,
+        else => return null,
+    };
+
+    const system_obj = switch (context_obj.get("System") orelse return null) {
+        .object => |o| o,
+        else => return null,
+    };
+
+    const api_endpoint = switch (system_obj.get("apiEndpoint") orelse return null) {
+        .string => |s| s,
+        else => return null,
+    };
+
+    const api_access_token = switch (system_obj.get("apiAccessToken") orelse return null) {
+        .string => |s| s,
+        else => return null,
+    };
+
+    const device_obj = switch (system_obj.get("device") orelse return null) {
+        .object => |o| o,
+        else => return null,
+    };
+
+    const device_id = switch (device_obj.get("deviceId") orelse return null) {
+        .string => |s| s,
+        else => return null,
+    };
+
+    return Context{
+        .api_endpoint = api_endpoint,
+        .api_access_token = api_access_token,
+        .device_id = device_id,
+    };
+}
+
+/// Fetch user's timezone from Alexa Settings API.
+/// GET {apiEndpoint}/v2/devices/{deviceId}/settings/System.timeZone
+/// Returns timezone name like "America/Los_Angeles" or null on failure.
+/// Caller owns the returned memory.
+pub fn fetchTimezone(
+    allocator: Allocator,
+    http_interface: homeassistant.HttpClientInterface,
+    context: Context,
+) ?[]const u8 {
+    const url = std.fmt.allocPrint(
+        allocator,
+        "{s}/v2/devices/{s}/settings/System.timeZone",
+        .{ context.api_endpoint, context.device_id },
+    ) catch {
+        log.warn("Failed to allocate Alexa Settings API URL", .{});
+        return null;
+    };
+    defer allocator.free(url);
+
+    const auth_header = std.fmt.allocPrint(
+        allocator,
+        "Bearer {s}",
+        .{context.api_access_token},
+    ) catch {
+        log.warn("Failed to allocate auth header", .{});
+        return null;
+    };
+    defer allocator.free(auth_header);
+
+    const headers = [_]http.Header{
+        .{ .name = "Authorization", .value = auth_header },
+    };
+
+    const result = http_interface.fetch(allocator, .{
+        .url = url,
+        .method = .GET,
+        .headers = &headers,
+        .body = null,
+    }) catch |err| {
+        log.warn("Alexa Settings API request failed: {}", .{err});
+        return null;
+    };
+    defer allocator.free(result.body);
+
+    if (result.status != .ok) {
+        log.warn("Alexa Settings API returned status: {}", .{result.status});
+        return null;
+    }
+
+    // Response is a JSON string like "America/Los_Angeles" (with quotes)
+    const parsed = json.parseFromSlice(json.Value, allocator, result.body, .{}) catch {
+        log.warn("Failed to parse Alexa Settings API response", .{});
+        return null;
+    };
+    defer parsed.deinit();
+
+    const timezone = switch (parsed.value) {
+        .string => |s| s,
+        else => {
+            log.warn("Alexa Settings API response is not a string", .{});
+            return null;
+        },
+    };
+
+    return allocator.dupe(u8, timezone) catch {
+        log.warn("Failed to allocate timezone string", .{});
+        return null;
+    };
+}
+
+// ============================================================================
+// Tests
+// ============================================================================
+
+test "parseContext with valid context" {
+    const json_str =
+        \\{
+        \\  "context": {
+        \\    "System": {
+        \\      "apiEndpoint": "https://api.amazonalexa.com",
+        \\      "apiAccessToken": "test-token-123",
+        \\      "device": {
+        \\        "deviceId": "amzn1.ask.device.XXXX"
+        \\      }
+        \\    }
+        \\  },
+        \\  "request": {}
+        \\}
+    ;
+
+    const parsed = try json.parseFromSlice(json.Value, std.testing.allocator, json_str, .{});
+    defer parsed.deinit();
+
+    const ctx = parseContext(parsed.value);
+    try std.testing.expect(ctx != null);
+    try std.testing.expectEqualStrings("https://api.amazonalexa.com", ctx.?.api_endpoint);
+    try std.testing.expectEqualStrings("test-token-123", ctx.?.api_access_token);
+    try std.testing.expectEqualStrings("amzn1.ask.device.XXXX", ctx.?.device_id);
+}
+
+test "parseContext with missing context" {
+    const json_str =
+        \\{
+        \\  "request": {}
+        \\}
+    ;
+
+    const parsed = try json.parseFromSlice(json.Value, std.testing.allocator, json_str, .{});
+    defer parsed.deinit();
+
+    const ctx = parseContext(parsed.value);
+    try std.testing.expect(ctx == null);
+}
diff --git a/src/homeassistant.zig b/src/homeassistant.zig
index 8f47a72..e837428 100644
--- a/src/homeassistant.zig
+++ b/src/homeassistant.zig
@@ -610,7 +610,7 @@ pub fn findEntitiesByName(
 }
 
 /// Format a detailed state response for an entity
-pub fn formatStateResponse(allocator: Allocator, entity: *const Entity) ![]const u8 {
+pub fn formatStateResponse(allocator: Allocator, entity: *const Entity, utc_offset: ?i32) ![]const u8 {
     var response: std.ArrayListUnmanaged(u8) = .empty;
     errdefer response.deinit(allocator);
 
@@ -631,13 +631,29 @@ pub fn formatStateResponse(allocator: Allocator, entity: *const Entity) ![]const
             try writer.print(". Target temperature is {d:.0} degrees", .{target});
         if (entity.current_temperature) |current|
             try writer.print(". Current temperature is {d:.0} degrees", .{current});
-    } else if (std.mem.eql(u8, entity.domain, "binary_sensor") or
+    }
+
+    // Add time since last change for lights, switches, binary sensors, and covers
+    if (std.mem.eql(u8, entity.domain, "light") or
+        std.mem.eql(u8, entity.domain, "switch") or
+        std.mem.eql(u8, entity.domain, "binary_sensor") or
         std.mem.eql(u8, entity.domain, "cover"))
     {
-        // Add time since last change if available
-        if (entity.last_changed) |lc|
-            if (parseTimeAgo(lc)) |ago|
-                try writer.print(" and has been {s} for {s}", .{ entity.state, ago });
+        if (entity.last_changed) |lc| {
+            if (parseTimestamp(lc)) |seconds| {
+                const duration = formatDuration(allocator, seconds) catch null;
+                const time_str = formatTimeFromTimestamp(allocator, lc, utc_offset) catch null;
+                if (duration) |dur| {
+                    defer allocator.free(dur);
+                    if (time_str) |ts| {
+                        defer allocator.free(ts);
+                        try writer.print(", and has been {s} for {s}, since {s}", .{ entity.state, dur, ts });
+                    } else {
+                        try writer.print(", and has been {s} for {s}", .{ entity.state, dur });
+                    }
+                }
+            }
+        }
     }
 
     try writer.writeAll(".");
@@ -645,15 +661,119 @@ pub fn formatStateResponse(allocator: Allocator, entity: *const Entity) ![]const
     return response.toOwnedSlice(allocator);
 }
 
-/// Parse ISO timestamp and return human-readable "time ago" string
-fn parseTimeAgo(iso_timestamp: []const u8) ?[]const u8 {
-    // Simple heuristic: check if it looks like an ISO timestamp
-    // In production, you'd parse this properly
-    if (iso_timestamp.len < 10) return null;
+/// Parse ISO timestamp and return duration in seconds since that time
+fn parseTimestamp(iso_timestamp: []const u8) ?i64 {
+    // Expected format: 2024-01-15T10:30:45.123456+00:00 or similar
+    if (iso_timestamp.len < 19) return null;
 
-    // For now, just return a generic message
-    // TODO: Implement proper time parsing
-    return "some time";
+    // Parse date components
+    const year = std.fmt.parseInt(u16, iso_timestamp[0..4], 10) catch return null;
+    if (iso_timestamp[4] != '-') return null;
+    const month = std.fmt.parseInt(u4, iso_timestamp[5..7], 10) catch return null;
+    if (iso_timestamp[7] != '-') return null;
+    const day = std.fmt.parseInt(u5, iso_timestamp[8..10], 10) catch return null;
+    if (iso_timestamp[10] != 'T') return null;
+    const hour = std.fmt.parseInt(u5, iso_timestamp[11..13], 10) catch return null;
+    if (iso_timestamp[13] != ':') return null;
+    const minute = std.fmt.parseInt(u6, iso_timestamp[14..16], 10) catch return null;
+    if (iso_timestamp[16] != ':') return null;
+    const second = std.fmt.parseInt(u6, iso_timestamp[17..19], 10) catch return null;
+
+    // Calculate days from epoch (1970-01-01)
+    // Count days for complete years
+    var days: i64 = 0;
+    var y: u16 = 1970;
+    while (y < year) : (y += 1) {
+        days += if (std.time.epoch.isLeapYear(y)) 366 else 365;
+    }
+
+    // Add days for complete months in current year
+    const months = [_]u5{ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+    var m: u4 = 1;
+    while (m < month) : (m += 1) {
+        days += months[m - 1];
+        if (m == 2 and std.time.epoch.isLeapYear(year)) days += 1;
+    }
+
+    // Add days in current month
+    days += day - 1;
+
+    const timestamp_epoch = days * std.time.s_per_day +
+        @as(i64, hour) * 3600 + @as(i64, minute) * 60 + @as(i64, second);
+
+    // Get current time
+    const now = std.time.timestamp();
+
+    return now - timestamp_epoch;
+}
+
+/// Format duration as human-readable string
+fn formatDuration(allocator: Allocator, seconds: i64) ![]const u8 {
+    if (seconds < 0) return try allocator.dupe(u8, "just now");
+
+    const minutes = @divFloor(seconds, 60);
+    const hours = @divFloor(minutes, 60);
+    const days = @divFloor(hours, 24);
+
+    if (days > 0) {
+        if (days == 1) {
+            const remaining_hours = @mod(hours, 24);
+            if (remaining_hours > 0) {
+                return try std.fmt.allocPrint(allocator, "1 day and {d} hour{s}", .{
+                    remaining_hours,
+                    if (remaining_hours == 1) "" else "s",
+                });
+            }
+            return try allocator.dupe(u8, "1 day");
+        }
+        return try std.fmt.allocPrint(allocator, "{d} days", .{days});
+    }
+
+    if (hours > 0) {
+        const remaining_minutes = @mod(minutes, 60);
+        if (remaining_minutes > 0) {
+            return try std.fmt.allocPrint(allocator, "{d} hour{s} and {d} minute{s}", .{
+                hours,
+                if (hours == 1) "" else "s",
+                remaining_minutes,
+                if (remaining_minutes == 1) "" else "s",
+            });
+        }
+        return try std.fmt.allocPrint(allocator, "{d} hour{s}", .{ hours, if (hours == 1) "" else "s" });
+    }
+
+    if (minutes > 0) {
+        return try std.fmt.allocPrint(allocator, "{d} minute{s}", .{ minutes, if (minutes == 1) "" else "s" });
+    }
+
+    if (seconds < 10) {
+        return try allocator.dupe(u8, "just now");
+    }
+
+    return try std.fmt.allocPrint(allocator, "{d} seconds", .{seconds});
+}
+
+/// Format time from ISO timestamp as "11:30 AM" style, adjusted for timezone.
+/// If utc_offset is null, returns error (caller should omit "since" time).
+fn formatTimeFromTimestamp(allocator: Allocator, iso_timestamp: []const u8, utc_offset: ?i32) ![]const u8 {
+    const offset = utc_offset orelse return error.NoTimezone;
+
+    if (iso_timestamp.len < 16) return error.InvalidTimestamp;
+
+    const hour_24_utc = std.fmt.parseInt(i32, iso_timestamp[11..13], 10) catch return error.InvalidTimestamp;
+    const minute = std.fmt.parseInt(u6, iso_timestamp[14..16], 10) catch return error.InvalidTimestamp;
+
+    // Apply timezone offset (offset is in seconds, convert to hours)
+    const offset_hours = @divTrunc(offset, 3600);
+    const hour_24_local = @mod(hour_24_utc + offset_hours + 24, 24);
+
+    const am_pm: []const u8 = if (hour_24_local < 12) "AM" else "PM";
+    const hour_12: i32 = if (hour_24_local == 0) 12 else if (hour_24_local > 12) hour_24_local - 12 else hour_24_local;
+
+    if (minute == 0) {
+        return try std.fmt.allocPrint(allocator, "{d} {s}", .{ hour_12, am_pm });
+    }
+    return try std.fmt.allocPrint(allocator, "{d}:{d:0>2} {s}", .{ hour_12, minute, am_pm });
 }
 
 /// Format the "which one?" clarification prompt
@@ -692,6 +812,7 @@ pub fn handleDeviceAction(
     action: Action,
     device_name: []const u8,
     value: ?f32,
+    utc_offset: ?i32,
 ) !ActionResult {
     // Fetch all entities
     const states_result = client.getStates() catch |err| {
@@ -822,7 +943,7 @@ pub fn handleDeviceAction(
                     };
                 },
                 .query_state => {
-                    const response = try formatStateResponse(allocator, entity);
+                    const response = try formatStateResponse(allocator, entity, utc_offset);
                     return ActionResult{
                         .speech = response,
                         .end_session = true,
@@ -986,7 +1107,7 @@ test "formatStateResponse light on with brightness" {
         .current_temperature = null,
     };
 
-    const response = try formatStateResponse(allocator, &entity);
+    const response = try formatStateResponse(allocator, &entity, null);
     defer allocator.free(response);
 
     try std.testing.expect(std.mem.indexOf(u8, response, "Bedroom Light") != null);
@@ -1007,7 +1128,7 @@ test "formatStateResponse light off" {
         .current_temperature = null,
     };
 
-    const response = try formatStateResponse(allocator, &entity);
+    const response = try formatStateResponse(allocator, &entity, null);
     defer allocator.free(response);
 
     try std.testing.expect(std.mem.indexOf(u8, response, "off") != null);
@@ -1027,7 +1148,7 @@ test "formatStateResponse climate with temperatures" {
         .current_temperature = 68.0,
     };
 
-    const response = try formatStateResponse(allocator, &entity);
+    const response = try formatStateResponse(allocator, &entity, null);
     defer allocator.free(response);
 
     try std.testing.expect(std.mem.indexOf(u8, response, "Thermostat") != null);
@@ -1145,7 +1266,7 @@ test "handleDeviceAction turn on light success" {
         mock.interface(),
     );
 
-    const result = try handleDeviceAction(allocator, &client, .turn_on, "bedroom", null);
+    const result = try handleDeviceAction(allocator, &client, .turn_on, "bedroom", null, null);
     defer allocator.free(result.speech);
 
     try std.testing.expect(std.mem.indexOf(u8, result.speech, "Turned on") != null);
@@ -1172,7 +1293,7 @@ test "handleDeviceAction device not found" {
         mock.interface(),
     );
 
-    const result = try handleDeviceAction(allocator, &client, .turn_on, "garage", null);
+    const result = try handleDeviceAction(allocator, &client, .turn_on, "garage", null, null);
     defer allocator.free(result.speech);
 
     try std.testing.expect(std.mem.indexOf(u8, result.speech, "couldn't find") != null);
@@ -1199,7 +1320,7 @@ test "handleDeviceAction multiple matches returns clarification" {
         mock.interface(),
     );
 
-    const result = try handleDeviceAction(allocator, &client, .turn_on, "light", null);
+    const result = try handleDeviceAction(allocator, &client, .turn_on, "light", null, null);
     defer allocator.free(result.speech);
 
     try std.testing.expect(std.mem.indexOf(u8, result.speech, "Which one") != null);
@@ -1227,7 +1348,7 @@ test "handleDeviceAction query state" {
         mock.interface(),
     );
 
-    const result = try handleDeviceAction(allocator, &client, .query_state, "bedroom", null);
+    const result = try handleDeviceAction(allocator, &client, .query_state, "bedroom", null, null);
     defer allocator.free(result.speech);
 
     try std.testing.expect(std.mem.indexOf(u8, result.speech, "Bedroom Light") != null);
@@ -1256,7 +1377,7 @@ test "handleDeviceAction set brightness" {
         mock.interface(),
     );
 
-    const result = try handleDeviceAction(allocator, &client, .set_value, "bedroom", 50.0);
+    const result = try handleDeviceAction(allocator, &client, .set_value, "bedroom", 50.0, null);
     defer allocator.free(result.speech);
 
     try std.testing.expect(std.mem.indexOf(u8, result.speech, "Set") != null);
diff --git a/src/main.zig b/src/main.zig
index 2948b9e..7c3bf0a 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -3,6 +3,8 @@ const json = std.json;
 const lambda = @import("lambda_runtime");
 const rinnai = @import("rinnai");
 const homeassistant = @import("homeassistant.zig");
+const alexa = @import("alexa.zig");
+const timezone = @import("timezone.zig");
 const Config = @import("Config.zig");
 const builtin = @import("builtin");
 
@@ -19,7 +21,7 @@ pub fn main() !u8 {
     // Check for --help first (no config needed)
     for (args) |arg| {
         if (std.mem.eql(u8, arg, "--help") or std.mem.eql(u8, arg, "-h")) {
-            printHelp() catch return 1;
+            printHelp(args) catch return 1;
             return 0;
         }
     }
@@ -84,7 +86,7 @@ fn handler(allocator: std.mem.Allocator, event_data: []const u8, config: Config)
     if (std.mem.eql(u8, request_type_str, "LaunchRequest")) {
         return buildAlexaResponse(allocator, "What would you like me to do? You can ask me to start the hot water, or control your smart home devices.", false);
     } else if (std.mem.eql(u8, request_type_str, "IntentRequest")) {
-        return handleIntentRequest(allocator, request_obj, config);
+        return handleIntentRequest(allocator, request_obj, parsed.value, config);
     } else if (std.mem.eql(u8, request_type_str, "SessionEndedRequest")) {
         return buildAlexaResponse(allocator, "", true);
     }
@@ -93,7 +95,7 @@ fn handler(allocator: std.mem.Allocator, event_data: []const u8, config: Config)
 }
 
 /// Handle Alexa intent requests
-fn handleIntentRequest(allocator: std.mem.Allocator, request_obj: json.Value, config: Config) ![]const u8 {
+fn handleIntentRequest(allocator: std.mem.Allocator, request_obj: json.Value, full_request: json.Value, config: Config) ![]const u8 {
     const intent_obj = request_obj.object.get("intent") orelse {
         if (!builtin.is_test) log.err("No 'intent' field in IntentRequest", .{});
         return buildAlexaResponse(allocator, "I couldn't understand your intent.", true);
@@ -116,7 +118,7 @@ fn handleIntentRequest(allocator: std.mem.Allocator, request_obj: json.Value, co
     } else if (std.mem.eql(u8, intent_name, "HomeAssistantIntent") or
         std.mem.eql(u8, intent_name, "SetDeviceValueIntent"))
     {
-        return handleHomeAssistantIntent(allocator, intent_obj, config);
+        return handleHomeAssistantIntent(allocator, intent_obj, full_request, config);
     } else if (std.mem.eql(u8, intent_name, "WeezTheJuiceIntent")) {
         return handleWeezTheJuice(allocator, config);
     } else if (std.mem.eql(u8, intent_name, "AMAZON.HelpIntent")) {
@@ -178,7 +180,7 @@ fn handleRecirculateWater(allocator: std.mem.Allocator, config: Config) ![]const
 }
 
 /// Handle the Home Assistant device control intent
-fn handleHomeAssistantIntent(allocator: std.mem.Allocator, intent_obj: json.Value, config: Config) ![]const u8 {
+fn handleHomeAssistantIntent(allocator: std.mem.Allocator, intent_obj: json.Value, full_request: json.Value, config: Config) ![]const u8 {
     // Get Home Assistant credentials from config
     const ha_url = config.home_assistant_url orelse {
         log.err("HOME_ASSISTANT_URL not configured", .{});
@@ -208,6 +210,12 @@ fn handleHomeAssistantIntent(allocator: std.mem.Allocator, intent_obj: json.Valu
     );
     defer client.deinit();
 
+    // Only resolve timezone for state queries (avoids unnecessary Alexa API calls)
+    const utc_offset: ?i32 = if (params.action == .query_state)
+        resolveTimezone(allocator, full_request, config)
+    else
+        null;
+
     // Execute the action
     const result = homeassistant.handleDeviceAction(
         allocator,
@@ -215,6 +223,7 @@ fn handleHomeAssistantIntent(allocator: std.mem.Allocator, intent_obj: json.Valu
         params.action,
         params.device_name,
         params.value,
+        utc_offset,
     ) catch |err| {
         log.err("Home Assistant error: {}", .{err});
         return buildAlexaResponse(allocator, "I had trouble communicating with Home Assistant. Please try again.", true);
@@ -248,6 +257,7 @@ fn handleWeezTheJuice(allocator: std.mem.Allocator, config: Config) ![]const u8
         .toggle,
         "bedroom",
         null,
+        null, // No timezone needed for toggle
     ) catch |err| {
         log.err("Home Assistant error: {}", .{err});
         return buildAlexaResponse(allocator, "I had trouble weezin' the juice.", true);
@@ -343,6 +353,38 @@ fn extractSlotNumber(slots: ?json.Value, slot_name: []const u8) ?f32 {
     return std.fmt.parseFloat(f32, value.string) catch null;
 }
 
+/// Resolve the UTC offset for timezone conversion.
+/// In Lambda mode: tries Alexa Settings API, then falls back to local timezone.
+/// In local mode: uses TZ env var or /etc/timezone.
+fn resolveTimezone(allocator: std.mem.Allocator, parsed_value: json.Value, config: Config) ?i32 {
+    // First try to get timezone from Alexa context (Lambda mode)
+    if (alexa.parseContext(parsed_value)) |context| {
+        // Need HTTP client for Alexa API
+        const ha_url = config.home_assistant_url orelse return resolveLocalTimezone(allocator);
+        const ha_token = config.home_assistant_token orelse return resolveLocalTimezone(allocator);
+
+        var ha_client = homeassistant.Client.init(allocator, ha_url, ha_token);
+        defer ha_client.deinit();
+
+        if (alexa.fetchTimezone(allocator, ha_client.http_interface, context)) |tz_name| {
+            defer allocator.free(tz_name);
+            if (timezone.getUtcOffset(allocator, tz_name)) |offset| {
+                return offset;
+            }
+        }
+    }
+
+    // Fall back to local timezone
+    return resolveLocalTimezone(allocator);
+}
+
+/// Resolve timezone from local system (TZ env var or /etc/timezone)
+fn resolveLocalTimezone(allocator: std.mem.Allocator) ?i32 {
+    const tz_name = timezone.getLocalTimezone(allocator) orelse return null;
+    defer allocator.free(tz_name);
+    return timezone.getUtcOffset(allocator, tz_name);
+}
+
 /// Build an Alexa skill response JSON
 fn buildAlexaResponse(allocator: std.mem.Allocator, speech: []const u8, end_session: bool) ![]const u8 {
     // Escape speech for JSON
@@ -378,9 +420,13 @@ fn buildAlexaResponse(allocator: std.mem.Allocator, speech: []const u8, end_sess
 // Local Testing Mode
 // =============================================================================
 
-fn printHelp() !void {
-    const help =
-        \\Usage: bootstrap [OPTIONS]
+fn printHelp(args: []const []const u8) !void {
+    const prog = std.fs.path.basename(args[0]);
+    var stdout_buffer: [4096]u8 = undefined;
+    var stdout_writer = std.fs.File.stdout().writer(&stdout_buffer);
+    const stdout = &stdout_writer.interface;
+    try stdout.print(
+        \\Usage: {0s} [OPTIONS]
         \\
         \\Alexa skill handler for water recirculation and Home Assistant control.
         \\Automatically detects Lambda environment via AWS_LAMBDA_RUNTIME_API.
@@ -405,16 +451,16 @@ fn printHelp() !void {
         \\  AMAZON.CancelIntent      Cancel/goodbye
         \\
         \\Examples:
-        \\  bootstrap --type=launch
-        \\  bootstrap --intent=RecirculateWaterIntent
-        \\  bootstrap --intent=HomeAssistantIntent --device="bedroom light" --action="turn on"
-        \\  bootstrap --intent=HomeAssistantIntent --device="bedroom light" --action="turn off"
-        \\  bootstrap --intent=HomeAssistantIntent --device="bedroom light" --action="toggle"
-        \\  bootstrap --intent=HomeAssistantIntent --device="bedroom light"
+        \\  {0s} --type=launch
+        \\  {0s} --intent=RecirculateWaterIntent
+        \\  {0s} --intent=HomeAssistantIntent --device="bedroom light" --action="turn on"
+        \\  {0s} --intent=HomeAssistantIntent --device="bedroom light" --action="turn off"
+        \\  {0s} --intent=HomeAssistantIntent --device="bedroom light" --action="toggle"
+        \\  {0s} --intent=HomeAssistantIntent --device="bedroom light"
         \\      (no action = query state)
-        \\  bootstrap --intent=SetDeviceValueIntent --device="bedroom light" --value=50
-        \\  bootstrap --intent=SetDeviceValueIntent --device="thermostat" --value=72
-        \\  bootstrap --intent=WeezTheJuiceIntent
+        \\  {0s} --intent=SetDeviceValueIntent --device="bedroom light" --value=50
+        \\  {0s} --intent=SetDeviceValueIntent --device="thermostat" --value=72
+        \\  {0s} --intent=WeezTheJuiceIntent
         \\
         \\Environment variables (or .env file in current directory):
         \\  COGNITO_USERNAME     Rinnai account username
@@ -422,11 +468,7 @@ fn printHelp() !void {
         \\  HOME_ASSISTANT_URL   Home Assistant URL (e.g., https://ha.example.com)
         \\  HOME_ASSISTANT_TOKEN Home Assistant long-lived access token
         \\
-    ;
-    var stdout_buffer: [4096]u8 = undefined;
-    var stdout_writer = std.fs.File.stdout().writer(&stdout_buffer);
-    const stdout = &stdout_writer.interface;
-    try stdout.print("{s}", .{help});
+    , .{prog});
     try stdout.flush();
 }
 
diff --git a/src/timezone.zig b/src/timezone.zig
new file mode 100644
index 0000000..5691d54
--- /dev/null
+++ b/src/timezone.zig
@@ -0,0 +1,230 @@
+//! Timezone utilities: TZif parsing and local timezone resolution.
+
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+
+const log = std.log.scoped(.timezone);
+
+/// Get UTC offset in seconds for a timezone name.
+/// Reads /usr/share/zoneinfo/{name} and parses TZif format.
+/// Returns null on any error (file not found, parse error, etc.)
+pub fn getUtcOffset(allocator: Allocator, timezone_name: []const u8) ?i32 {
+    const path = std.fmt.allocPrint(allocator, "/usr/share/zoneinfo/{s}", .{timezone_name}) catch {
+        log.warn("Failed to allocate timezone path", .{});
+        return null;
+    };
+    defer allocator.free(path);
+
+    const file = std.fs.openFileAbsolute(path, .{}) catch {
+        log.warn("Failed to open timezone file: {s}", .{path});
+        return null;
+    };
+    defer file.close();
+
+    const data = file.readToEndAlloc(allocator, 64 * 1024) catch {
+        log.warn("Failed to read timezone file: {s}", .{path});
+        return null;
+    };
+    defer allocator.free(data);
+
+    return parseTzif(data);
+}
+
+/// Get local timezone name from environment.
+/// Checks TZ env var first, then reads /etc/timezone.
+/// Returns owned slice that caller must free, or null if not found.
+pub fn getLocalTimezone(allocator: Allocator) ?[]const u8 {
+    // First check TZ environment variable
+    if (std.process.getEnvVarOwned(allocator, "TZ")) |tz| {
+        // TZ can be a path like ":/etc/localtime" or just a name like "America/Los_Angeles"
+        // Strip leading colon if present
+        if (tz.len > 0 and tz[0] == ':') {
+            const stripped = allocator.dupe(u8, tz[1..]) catch {
+                allocator.free(tz);
+                return null;
+            };
+            allocator.free(tz);
+            return stripped;
+        }
+        return tz;
+    } else |_| {}
+
+    // Fall back to /etc/timezone
+    const file = std.fs.openFileAbsolute("/etc/timezone", .{}) catch {
+        log.warn("No TZ env var and failed to open /etc/timezone", .{});
+        return null;
+    };
+    defer file.close();
+
+    const content = file.readToEndAlloc(allocator, 256) catch {
+        log.warn("Failed to read /etc/timezone", .{});
+        return null;
+    };
+
+    // Trim trailing newline
+    const trimmed = std.mem.trimRight(u8, content, "\n\r \t");
+    if (trimmed.len == content.len) {
+        return content;
+    }
+
+    const result = allocator.dupe(u8, trimmed) catch {
+        allocator.free(content);
+        return null;
+    };
+    allocator.free(content);
+    return result;
+}
+
+/// Parse TZif binary file format.
+/// Returns most recent UTC offset in seconds, or null on error.
+fn parseTzif(data: []const u8) ?i32 {
+    // TZif header is 44 bytes minimum
+    if (data.len < 44) {
+        log.warn("TZif file too small: {d} bytes", .{data.len});
+        return null;
+    }
+
+    // Check magic number "TZif"
+    if (!std.mem.eql(u8, data[0..4], "TZif")) {
+        log.warn("Invalid TZif magic number", .{});
+        return null;
+    }
+
+    const version = data[4];
+
+    // Parse header counts (big-endian)
+    // Header layout:
+    // 0-3: magic "TZif"
+    // 4: version (0, '2', or '3')
+    // 5-19: reserved (15 bytes)
+    // 20-23: tzh_ttisutcnt
+    // 24-27: tzh_ttisstdcnt
+    // 28-31: tzh_leapcnt
+    // 32-35: tzh_timecnt
+    // 36-39: tzh_typecnt
+    // 40-43: tzh_charcnt
+    const tzh_ttisutcnt = std.mem.readInt(u32, data[20..24], .big);
+    const tzh_ttisstdcnt = std.mem.readInt(u32, data[24..28], .big);
+    const tzh_leapcnt = std.mem.readInt(u32, data[28..32], .big);
+    const tzh_timecnt = std.mem.readInt(u32, data[32..36], .big);
+    const tzh_typecnt = std.mem.readInt(u32, data[36..40], .big);
+    const tzh_charcnt = std.mem.readInt(u32, data[40..44], .big);
+
+    if (tzh_typecnt == 0) {
+        log.warn("TZif file has no time types", .{});
+        return null;
+    }
+
+    // For v2/v3 files, skip v1 data and parse v2 header
+    // v1 uses 4-byte transition times, v2/v3 use 8-byte
+    if (version == '2' or version == '3') {
+        // Calculate size of v1 data block to skip
+        const v1_data_size = tzh_timecnt * 4 + // transition times (4 bytes each in v1)
+            tzh_timecnt + // transition types (1 byte each)
+            tzh_typecnt * 6 + // ttinfos (6 bytes each)
+            tzh_charcnt + // timezone abbreviations
+            tzh_leapcnt * 8 + // leap second records (4+4 in v1)
+            tzh_ttisstdcnt + // std/wall indicators
+            tzh_ttisutcnt; // ut/local indicators
+
+        const v2_header_start = 44 + v1_data_size;
+
+        if (data.len < v2_header_start + 44) {
+            log.warn("TZif v2 file truncated", .{});
+            return null;
+        }
+
+        // Verify v2 header magic
+        if (!std.mem.eql(u8, data[v2_header_start..][0..4], "TZif")) {
+            log.warn("Invalid TZif v2 header magic", .{});
+            return null;
+        }
+
+        // Parse v2 header
+        const v2_timecnt = std.mem.readInt(u32, data[v2_header_start + 32 ..][0..4], .big);
+        const v2_typecnt = std.mem.readInt(u32, data[v2_header_start + 36 ..][0..4], .big);
+
+        if (v2_typecnt == 0) {
+            log.warn("TZif v2 has no time types", .{});
+            return null;
+        }
+
+        // Calculate offset to ttinfo structures in v2 data
+        const v2_data_start = v2_header_start + 44;
+        const ttinfo_offset = v2_data_start +
+            v2_timecnt * 8 + // transition times (8 bytes each in v2)
+            v2_timecnt; // transition types (1 byte each)
+
+        return readLastTtinfoOffset(data, ttinfo_offset, v2_typecnt);
+    }
+
+    // v1 format: ttinfos start after transition times and types
+    const ttinfo_offset = 44 +
+        tzh_timecnt * 4 + // transition times
+        tzh_timecnt; // transition types
+
+    return readLastTtinfoOffset(data, ttinfo_offset, tzh_typecnt);
+}
+
+/// Read the UTC offset from ttinfo structures.
+/// Finds the first non-DST entry with a "normal" offset (multiple of 15 min), or falls back to first entry.
+/// Each ttinfo is 6 bytes: i32 offset, u8 is_dst, u8 abbr_idx
+fn readLastTtinfoOffset(data: []const u8, ttinfo_offset: usize, typecnt: u32) ?i32 {
+    if (data.len < ttinfo_offset + 6) {
+        log.warn("TZif file truncated at ttinfo", .{});
+        return null;
+    }
+
+    // Look for a non-DST entry (standard time) with a "normal" offset
+    // Skip historical LMT entries which often have unusual offsets
+    var i: usize = 0;
+    while (i < typecnt) : (i += 1) {
+        const off = ttinfo_offset + i * 6;
+        if (data.len < off + 6) break;
+
+        const offset = std.mem.readInt(i32, data[off..][0..4], .big);
+        const is_dst = data[off + 4];
+
+        // Skip DST entries
+        if (is_dst != 0) continue;
+
+        // Skip unusual offsets (not multiples of 15 minutes = 900 seconds)
+        // This filters out historical LMT entries
+        if (@mod(offset, 900) != 0) continue;
+
+        // Sanity check: offset should be reasonable (-14 to +14 hours)
+        if (offset >= -14 * 3600 and offset <= 14 * 3600) {
+            return offset;
+        }
+    }
+
+    // Fall back to first entry if no suitable entry found
+    const offset = std.mem.readInt(i32, data[ttinfo_offset..][0..4], .big);
+
+    // Sanity check
+    if (offset < -14 * 3600 or offset > 14 * 3600) {
+        log.warn("TZif offset out of range: {d}", .{offset});
+        return null;
+    }
+
+    return offset;
+}
+
+// ============================================================================
+// Tests
+// ============================================================================
+
+test "getLocalTimezone with TZ env var" {
+    // This test depends on environment, just verify it doesn't crash
+    const allocator = std.testing.allocator;
+    if (getLocalTimezone(allocator)) |tz| {
+        defer allocator.free(tz);
+        try std.testing.expect(tz.len > 0);
+    }
+}
+
+test "parseTzif with invalid data" {
+    try std.testing.expectEqual(null, parseTzif(""));
+    try std.testing.expectEqual(null, parseTzif("short"));
+    try std.testing.expectEqual(null, parseTzif("NotTZif" ++ "\x00" ** 37));
+}