fix flaky tests

src/cache/store.zig

@@ -2740,11 +2740,15 @@ test "writeSupplement Dividend: no existing file establishes an initial TTL" {
 
     var s = Store.init(io, allocator, dir_path);
 
-    const now_s = std.Io.Timestamp.now(io, .real).toSeconds();
+    // Bracket the write: `writeSupplement` reads the clock itself, so
+    // an instant captured only before it can be a second behind the
+    // one it stamps, which flakes the upper bound below.
+    const before_s = std.Io.Timestamp.now(io, .real).toSeconds();
     var incoming = [_]Dividend{
         .{ .ex_date = Date.fromYmd(2024, 5, 15), .amount = 0.50 },
     };
     s.writeSupplement(Dividend, "TEST", incoming[0..], "tiingo");
+    const after_s = std.Io.Timestamp.now(io, .real).toSeconds();
 
     const path = try std.fs.path.join(allocator, &.{ dir_path, "TEST", "dividends.srf" });
     defer allocator.free(path);
@@ -2760,8 +2764,8 @@ test "writeSupplement Dividend: no existing file establishes an initial TTL" {
     const spec = DataType.dividends.ttl();
     const jitter = @divFloor(spec.seconds * @as(i64, spec.jitter_pct), 100);
     const new_expires = it.expires orelse return error.ExpiresMissing;
-    try std.testing.expect(new_expires - now_s >= spec.seconds - jitter);
-    try std.testing.expect(new_expires - now_s <= spec.seconds + jitter);
+    try std.testing.expect(new_expires - before_s >= spec.seconds - jitter);
+    try std.testing.expect(new_expires - after_s <= spec.seconds + jitter);
 }
 
 test "writeMerged Dividend: field-level upgrade fills nulls (Tiingo-then-Polygon)" {

src/service.zig

@@ -5485,24 +5485,43 @@ test "dividendTtl: the chosen clock is what actually lands on disk" {
 
     var store = cache.Store.init(io, allocator, dir_path);
     const today = fmt.todayDate(io);
-    const now_s = std.Io.Timestamp.now(io, .real).toSeconds();
+
+    // `store.write` reads the clock itself, so a single `now` captured
+    // here can be a second behind the one it stamps - which flaked this
+    // test as `expected 516344, found 516345`. Bracket each write
+    // instead: the stamped expiry must be `offset` past SOME instant in
+    // [before, after].
+    const Bracket = struct {
+        fn expect(expires: i64, offset: i64, before_s: i64, after_s: i64) !void {
+            try std.testing.expect(expires >= before_s + offset);
+            try std.testing.expect(expires <= after_s + offset);
+        }
+    };
 
     // Established payer -> ~14 days.
     var established = quarterlySeries(6, today.addDays(-30), 91);
+    const long_before = std.Io.Timestamp.now(io, .real).toSeconds();
     store.write(Dividend, "TESTA", established[0..], DataService.dividendTtl(&established));
+    const long_after = std.Io.Timestamp.now(io, .real).toSeconds();
     const long_expires = readExpires(io, allocator, dir_path, "TESTA") orelse return error.TestUnexpectedResult;
-    try std.testing.expectEqual(
+    try Bracket.expect(
+        long_expires,
         cache.computeExpires(0, DataService.dividendTtl(&established), "TESTA"),
-        long_expires - now_s,
+        long_before,
+        long_after,
     );
 
     // Sparse history -> ~6 days.
     var sparse = divsFromYmd(.{ .{ 2026, 6, 15 }, .{ 2026, 3, 17 } });
+    const short_before = std.Io.Timestamp.now(io, .real).toSeconds();
     store.write(Dividend, "TESTB", sparse[0..], DataService.dividendTtl(&sparse));
+    const short_after = std.Io.Timestamp.now(io, .real).toSeconds();
     const short_expires = readExpires(io, allocator, dir_path, "TESTB") orelse return error.TestUnexpectedResult;
-    try std.testing.expectEqual(
+    try Bracket.expect(
+        short_expires,
         cache.computeExpires(0, DataService.dividendTtl(&sparse), "TESTB"),
-        short_expires - now_s,
+        short_before,
+        short_after,
     );
 
     // And the long one really is longer, so nobody can "simplify" the two