Just keep in mind that the time is GMT, so if you remember that you joined around late evening EST, for example, that shifts the date. You can use a time zone converter to get the correct time in GMT.
Like what Stars said, you can convert real world datetime to Glitch datetime using that tool. To find out when you joined in real world time, check your account history and look for the 100 credits given to new players. Remember to take into account timezones - PST is GMT -7.