wttr/scripts

Scripts

generate_timezone_table.py

Generates src/location/timezone_offsets.zig with a lookup table mapping longitude to timezone offset.

How it works:

• Samples 360 longitudes (-180° to 179°) at 3 latitudes (0°, 30°N, 30°S)
• For each longitude, queries timezonefinder library for timezone at each latitude
• Uses the most common timezone offset across the 3 latitudes (handles political boundaries like China)
• Generates a [360]i16 array with offsets in minutes from UTC

Usage:

./scripts/generate_timezone_table.py

Requirements:

• Uses uv with inline script dependencies (no manual installation needed)
• Takes ~10-20 seconds to generate

Accuracy:

• Works well for mid-latitudes (±30°) where most population lives
• Can be off by 1-2.5 hours at extreme latitudes (e.g., Russia vs Australia at same longitude)
• Acceptable for "morning/afternoon/evening/night" weather labels
• If higher accuracy is needed, modify getTimezoneOffset() to use latitude

Why this approach:

• O(1) lookup, no complex calculations at runtime
• Handles political boundaries (e.g., China's UTC+8 across all longitudes)
• Simple to regenerate with different latitude samples if needed
• API accepts Coordinates (not just longitude) for future improvements