I'm working on a website called Kalkulator Jadian, a simple relationship-date calculator that calculates how long two people have been together from their starting date.
The calculator shows the duration in days, hours, minutes, and seconds. I'm currently looking at the best way to handle date and time calculations when users access the tool from different countries and time zones.
For example, if someone enters a relationship date without a specific time, should the application treat it as midnight in the user's local time zone, UTC, or use another approach?
I'd appreciate advice from developers who have dealt with date/time calculations in web applications. What approach would you recommend for keeping the results consistent and avoiding unexpected differences between users?
I'm particularly interested in practical JavaScript implementation and time zone-handling suggestions.
