在 flutter 日期范围选择器中将两个日期之间的所有日期作为列表返回

Question

I got only two dates form flutter date_range_picker but I want a list of date between two selected dates. Thanks for your answers

Answer 1

Try the following:

List<DateTime> getDaysInBeteween(DateTime startDate, DateTime endDate) {
    List<DateTime> days = [];
    for (int i = 0; i <= endDate.difference(startDate).inDays; i++) {
      days.add(startDate.add(Duration(days: i)));
    }
    return days;
  }

Answer 2

There is a problem with the accepted solution. The code will run fine most of the time but it will fail because this doesn't considers Daylight saving time (DST) / Daylight time / Summer Time ( https://en.wikipedia.org/wiki/Daylight_saving_time ).

As a result, for example it will generate the following sequence (notice the gap):

2020-10-24 00:00:00.000
2020-10-25 00:00:00.000
2020-10-25 23:00:00.000 # Mind the Gap :)
2020-10-26 23:00:00.000

Here it is an alternative solution that will work better, I think.

List<DateTime> getDaysInBeteween(DateTime startDate, DateTime endDate) {
    List<DateTime> days = [];
    for (int i = 0; i <= endDate.difference(startDate).inDays; i++) {
      days.add(
        DateTime(
          startDate.year, 
          startDate.month, 
          // In Dart you can set more than. 30 days, DateTime will do the trick
          startDate.day + i)
      );
    }
    return days;
}

Answer 3

I always do like this:

final today = DateTime.now();
final monthAgo = DateTime(today.year, today.month - 1, today.day);

final List<DateTime> days = [];
for (int i = 0; i <= today.difference(monthAgo).inDays; i++) {
  days.add(monthAgo.add(Duration(days: i)));
}

Answer 4

Always use UTC to avoid issues like DST when working with dates such as addition or subtraction and then convert them back to local time.

Also, adding days manually like day + 1 could cause issues if both the start and end dates are not of the same month.

So to avoid all that do it like this:-

Case 1 - Get days in between including start and end Date:-

List<DateTime> getDaysInBetweenIncludingStartEndDate(
    {required DateTime startDateTime, required DateTime endDateTime}) {

  // Converting dates provided to UTC
  // So that all things like DST don't affect subtraction and addition on dates
  DateTime startDateInUTC =
      DateTime.utc(startDateTime.year, startDateTime.month, startDateTime.day);
  DateTime endDateInUTC =
      DateTime.utc(endDateTime.year, endDateTime.month, endDateTime.day);

  // Created a list to hold all dates
  List<DateTime> daysInLocalFormat = [];
  
  // Starting a loop with the initial value as the Start Date
  // With an increment of 1 day on each loop
  // With condition current value of loop is smaller than or same as end date
  for (DateTime i = startDateInUTC;
      i.isBefore(endDateInUTC) || i.isAtSameMomentAs(endDateInUTC);
      i = i.add(const Duration(days: 1))) {
    
    // Converting back UTC date to Local date before inserting in list
    // You can keep in UTC format depending on your case
    daysInLocalFormat.add(DateTime(i.year, i.month, i.day));
    
  }
  return daysInLocalFormat;
}

Case 2 - Get days in between excluding start and end Date:-

List<DateTime> getDaysInBetweenExcludingStartEndDate(
    {required DateTime startDateTime, required DateTime endDateTime}) {

  // Converting dates provided to UTC
  // So that all things like DST don't affect subtraction and addition on dates
  DateTime startDateInUTC =
      DateTime.utc(startDateTime.year, startDateTime.month, startDateTime.day);
  DateTime endDateInUTC =
      DateTime.utc(endDateTime.year, endDateTime.month, endDateTime.day);

  // Created a list to hold all dates
  List<DateTime> daysInLocalFormat = [];
  
  // Starting a loop with the initial value as the next day of the Start Date
  // With an increment of 1 day on each loop
  // With condition current value of loop is smaller than end date
  for (DateTime i = startDateInUTC.add(const Duration(days: 1));
      i.isBefore(endDateInUTC);
      i = i.add(const Duration(days: 1))) {

    // Converting back UTC date to Local date before inserting in list
    // You can keep in UTC format depending on your case
    daysInLocalFormat.add(DateTime(i.year, i.month, i.day));
  }

  return daysInLocalFormat;
}