DateTime.Now and Culture/Timezone specific

Question

Our application was designed to handle user from different Geographic location.

We are unable to detect what is the current end user local time and

Answer 1

Standard approach is to always store any time data as UTC if particular moment in time is important. That time is not impacted by time zone changes and cultures.

Most common approach to showing time with time zone is to store time as UTC and convert to current user's culture/time zone combination when you display the value. This approach only requires single date time filed in the storage.

Note that for Web cases (like ASP.Net) you may need to figure out user's culture/time zone first and send it to server (as this information is not necessary available on GET requests) or do formatting of time in the browser.

Depending what "show the same history time" you may need to store additional information like current culture and/or current offset. If you need to show time exactly as original user seen it you may also save string representation (because formats/translations can change later and value will look different, also it is unusual).

Note: culture and time zone are not tied together, so you'll need to decide how you need to handle cases like IN-IN culture in US PST time zone.