How can I tell if DateTime.Now() is on a day AFTER a different DateTime

Question

I\'m running this on flutter, but I guess this could be a more general issue.

I am saving a DateTime in the preferences. I want to be able to then tell if DateTime

Answer 1

I would compute the difference between midnight of the day of the last timestamp and midnight of the current timestamp. That is, consider only the date portion of a DateTime and ignore the time.

DateTime date(DateTime dateTime) =>
    DateTime(dateTime.year, dateTime.month, dateTime.day);

// Intentionally check for a positive difference in hours instead of days
// so we don't need to worry about 23-hour days from DST.  Any non-zero
// number of hours here means a difference of at least a "day".
if (date(DateTime.now()).difference(date(lastDailyCheck)).inHours > 0) {
  // "One day" after.
}

If you're using UTC timestamps and don't care about when midnight is in whatever the local time is, the comparison could more intuitively use .inDays >= 1.