Handle dates and timezones correctly

Handle date and timezone calculations

Ensuring correct cross-timezone scheduling and temporal calculations without off-by-one errors.

• · Date/time values, source timezone, target timezone, duration/offset operations

• · Correct date/time value, handling of DST transitions, ISO 8601 serialization

• · Timezone database (IANA tzdata)
• · Language-specific date libraries

Timezone identifiers known (e.g., America/New_York); source and target zones specified

DST transition mishandled (spring forward, fall back); UTC offset alone insufficient; naive datetime comparison fails across zones

• · DST transition handling specified
• · ISO 8601 format preference
• · Naive datetime anti-pattern clearly marked