@TanyaS58

Store every send time in UTC, but save each user’s IANA time zone like America New York or Asia Kolkata on their profile. When you plan a campaign, calculate each user’s target local time with a time zone library so daylight saving is handled for you. Convert that local time back to UTC and schedule one email job per user for that exact UTC timestamp. Use a scheduler or queue that wakes up often, pulls items whose due time is now or past, and sends them. If you have many users, batch by time zone or by the next hour to keep throughput steady. Let users set quiet hours and skip any send that would hit those hours in their local time. For unknown time zones, infer from country or last login offset, or fall back to a safe default. Log both the intended local time and the actual send time in UTC so you can audit and debug edge cases like daylight saving changes. Test with cases around 1 AM to 3 AM and around DST change dates to make sure nothing is missed or double sent.