How to display time ago like Youtube in Flutter

I've created an extension on String

 extension StringExtension on String {
  static String displayTimeAgoFromTimestamp(String timestamp) {
    final year = int.parse(timestamp.substring(0, 4));
    final month = int.parse(timestamp.substring(5, 7));
    final day = int.parse(timestamp.substring(8, 10));
    final hour = int.parse(timestamp.substring(11, 13));
    final minute = int.parse(timestamp.substring(14, 16));

    final DateTime videoDate = DateTime(year, month, day, hour, minute);
    final int diffInHours = DateTime.now().difference(videoDate).inHours;

    String timeAgo = '';
    String timeUnit = '';
    int timeValue = 0;

    if (diffInHours < 1) {
      final diffInMinutes = DateTime.now().difference(videoDate).inMinutes;
      timeValue = diffInMinutes;
      timeUnit = 'minute';
    } else if (diffInHours < 24) {
      timeValue = diffInHours;
      timeUnit = 'hour';
    } else if (diffInHours >= 24 && diffInHours < 24 * 7) {
      timeValue = (diffInHours / 24).floor();
      timeUnit = 'day';
    } else if (diffInHours >= 24 * 7 && diffInHours < 24 * 30) {
      timeValue = (diffInHours / (24 * 7)).floor();
      timeUnit = 'week';
    } else if (diffInHours >= 24 * 30 && diffInHours < 24 * 12 * 30) {
      timeValue = (diffInHours / (24 * 30)).floor();
      timeUnit = 'month';
    } else {
      timeValue = (diffInHours / (24 * 365)).floor();
      timeUnit = 'year';
    }

    timeAgo = timeValue.toString() + ' ' + timeUnit;
    timeAgo += timeValue > 1 ? 's' : '';

    return timeAgo + ' ago';
  }
}

Then call in text:

StringExtension.displayTimeAgoFromTimestamp(video.timestamp)

You can use the timeago package

example code below

import 'package:timeago/timeago.dart' as timeago;

main() {
    final fifteenAgo = new DateTime.now().subtract(new Duration(minutes: 15));

    print(timeago.format(fifteenAgo)); // 15 minutes ago
    print(timeago.format(fifteenAgo, locale: 'en_short')); // 15m
    print(timeago.format(fifteenAgo, locale: 'es')); // hace 15 minutos
}

to use it with the YYYY-MM-DDTHH:MM:SSZ time format you can convert the String to a DateTime then perform the operation on the DateTime variable

DateTime time = DateTime.parse("2020-07-12T20:42:19Z");
print(timeago.format(time));