I need to help with my fluter code,
I have an API its response me a date as a String
{"time": "12/04/2020 16:09:33"}
and I get the current time in my code from the phone using
var now = new DateTime.now();
how I can calculate the difference between two date-time???
You can use the intl library.
import 'package:intl/intl.dart';
String formatDuration(Duration duration) {
return duration.toString().split('.').first.padLeft(8, '0');
}
final s = "12/04/2020 16:09:33";
final formatter = DateFormat('dd/MM/yyyy HH:mm:ss');
final dateTime = formatter.parse(s);
var now = DateTime.now();
var difference = now.difference(dateTime);
print(formatDuration(difference));
print result ex. 53:37:11
You can achieve that using difference() method which accepts date as DateTime object. Hence, first you need to convert your input date which is in String format, into DateTime. Working code below:
String date = "12/04/2020 16:09:33";
DateFormat dateFormat = DateFormat("yyyy/MM/dd HH:mm:ss");
DateTime dateTime = dateFormat.parse(date); // converts into Datetime
var nowDate = DateTime.now();
var difference = nowDate.difference(dateTime);
print(difference); // 17553602:53:49.047936
How do I get the current week of the month as a number in Dart? I need to create some sort of calender with a week view where it says something like "2. Week of January"
You can use DateTime().now() to get the current time and date of the system or today's date also. Here is the code snippet below:
// Current date and time of system
String date = DateTime.now().toString();
// This will generate the time and date for first day of month
String firstDay = date.substring(0, 8) + '01' + date.substring(10);
// week day for the first day of the month
int weekDay = DateTime.parse(firstDay).weekday;
DateTime testDate = DateTime.now();
int weekOfMonth;
// If your calender starts from Monday
weekDay--;
weekOfMonth = ((testDate.day + weekDay) / 7).ceil();
print('Week of the month: $weekOfMonth');
weekDay++;
// If your calender starts from sunday
if (weekDay == 7) {
weekDay = 0;
}
weekOfMonth = ((testDate.day + weekDay) / 7).ceil();
print('Week of the month: $weekOfMonth');
Alternatively, if are looking for a complete implementation of the calender month UI then click here
My Answer is impaired from #dblank answer
extension DateTimeExtension on DateTime {
int get weekOfMonth {
var date = this;
final firstDayOfTheMonth = DateTime(date.year, date.month, 1);
int sum = firstDayOfTheMonth.weekday - 1 + date.day;
if (sum % 7 == 0) {
return sum ~/ 7;
} else {
return sum ~/ 7 + 1;
}
}
}
Then use it like this:
var wom = DateTime.now().weekOfMonth;
extension DateTimeExtension on DateTime {
int get weekOfMonth {
var wom = 0;
var date = this;
while (date.month == month) {
wom++;
date = date.subtract(const Duration(days: 7));
}
return wom;
}
}
Then use it like this:
var wom = DateTime.now().weekOfMonth;
I saw that in dart there is a class Duration but it cant be used add/subtract years or month. How did you managed this issue, I need to subtract 6 months from an date. Is there something like moment.js for dart or something around?
Thank you
Okay so you can do that in two steps, taken from #zoechi (a big contributor to Flutter):
Define the base time, let us say:
var date = new DateTime(2018, 1, 13);
Now, you want the new date:
var newDate = new DateTime(date.year, date.month - 1, date.day);
And you will get
2017-12-13
You can use the subtract and add methods
date1.subtract(Duration(days: 7, hours: 3, minutes: 43, seconds: 56));
date1.add(Duration(days: 1, hours: 23)));
Flutter Docs:
Subtract
Add
Try out this package, Jiffy. Adds and subtracts date time with respect to how many days there are in a month and also leap years. It follows the simple syntax of momentjs
You can add and subtract using the following units
years, months, weeks, days, hours, minutes, seconds and milliseconds
To add 6 months
DateTime d = Jiffy().add(months: 6).dateTime; // 2020-04-26 10:05:57.469367
// You can also add you own Datetime object
DateTime d = Jiffy(DateTime(2018, 1, 13)).add(months: 6).dateTime; // 2018-07-13 00:00:00.000
You can also do chaining using dart method cascading
var jiffy = Jiffy().add(months: 5, years: 1);
DateTime d = jiffy.dateTime; // 2021-03-26 10:07:10.316874
// you can also format with ease
String s = jiffy.format("yyyy, MMM"); // 2021, Mar
// or default formats
String s = jiffy.yMMMMEEEEdjm; // Friday, March 26, 2021 10:08 AM
You can use subtract and add methods
Subtract
Add
But you have to reassign the result to the variable, which means:
This wouldn't work
date1.add(Duration(days: 1, hours: 23)));
But this will:
date1 = date1.add(Duration(days: 1, hours: 23)));
For example:
void main() {
var d = DateTime.utc(2020, 05, 27, 0, 0, 0);
d.add(Duration(days: 1, hours: 23));
// the prev line has no effect on the value of d
print(d); // prints: 2020-05-27 00:00:00.000Z
//But
d = d.add(Duration(days: 1, hours: 23));
print(d); // prints: 2020-05-28 23:00:00.000Z
}
Dartpad link
In simple way without using any lib you can add Month and Year
var date = new DateTime(2021, 1, 29);
Adding Month :-
date = DateTime(date.year, date.month + 1, date.day);
Adding Year :-
date = DateTime(date.year + 1, date.month, date.day);
Not so simple.
final date = DateTime(2017, 1, 1);
final today = date.add(const Duration(days: 1451));
This results in 2020-12-21 23:00:00.000 because Dart considers daylight to calculate dates (so my 1451 days is missing 1 hour, and this is VERY dangerous (for example: Brazil abolished daylight savings in 2019, but if the app was written before that, the result will be forever wrong, same goes if the daylight savings is reintroduced in the future)).
To ignore the dayligh calculations, do this:
final date = DateTime(2017, 1, 1);
final today = DateTime(date.year, date.month, date.day + 1451);
Yep. Day is 1451 and this is OK. The today variable now shows the correct date and time: 2020-12-12 00:00:00.000.
It's pretty straightforward.
Simply add or subtract with numbers on DateTime parameters based on your requirements.
For example -
~ Here I had a requirement of getting the date-time exactly 16 years before today even with milliseconds and in the below way I got my solution.
DateTime today = DateTime.now();
debugPrint("Today's date is: $today"); //Today's date is: 2022-03-17 09:08:33.891843
After desired subtraction;
DateTime desiredDate = DateTime(
today.year - 16,
today.month,
today.day,
today.hour,
today.minute,
today.second,
today.millisecond,
today.microsecond,
);
debugPrint("16 years ago date is: $desiredDate"); // 16 years before date is: 2006-03-17 09:08:33.891843
Increase and Decrease of the day/month/year can be done by DateTime class
Initialise DateFormat which needed to be shown
var _inputFormat = DateFormat('EE, d MMM yyyy');
var _selectedDate = DateTime.now();
Increase Day/month/year:
_selectedDate = DateTime(_selectedDate.year,
_selectedDate.month + 1, _selectedDate.day);
Increase Day/month/year:
_selectedDate = DateTime(_selectedDate.year,
_selectedDate.month - 1, _selectedDate.day);
Above example is for only month, similar way we can increase or decrease year and day.
Can subtract any count of months.
DateTime subtractMonths(int count) {
var y = count ~/ 12;
var m = count - y * 12;
if (m > month) {
y += 1;
m = month - m;
}
return DateTime(year - y, month - m, day);
}
Also works
DateTime(date.year, date.month + (-120), date.day);
Future<void> main() async {
final DateTime now = DateTime.now();
var kdate = KDate.buildWith(now);
log("YEAR", kdate.year);
log("MONTH", kdate.month);
log("DATE", kdate.date);
log("Last Year", kdate.lastYear);
log("Last Month", kdate.lastMonth);
log("Yesturday", kdate.yesturday);
log("Last Week Date", kdate.lastWeekDate);
}
void log(title, data) {
print("\n$title ====> $data");
}
class KDate {
KDate({
this.now,
required this.year,
required this.month,
required this.date,
required this.lastYear,
required this.lastMonth,
required this.yesturday,
required this.lastWeekDate,
});
final DateTime? now;
final String? year;
final String? month;
final String? date;
final String? lastMonth;
final String? lastYear;
final String? yesturday;
final String? lastWeekDate;
factory KDate.buildWith(DateTime now) => KDate(
now: now,
year: (now.year).toString().split(" ")[0],
month: (now.month).toString().split(" ")[0],
date: (now.day).toString().split(" ")[0],
lastYear: (now.year - 1).toString().split(" ")[0],
lastMonth: DateTime(now.year, now.month, now.month)
.subtract(Duration(days: 28))
.toString()
.split(" ")[0]
.toString()
.split("-")[1],
yesturday: DateTime(now.year, now.month, now.day)
.subtract(Duration(days: 1))
.toString()
.split(" ")[0]
.toString()
.split("-")
.last,
lastWeekDate: DateTime(now.year, now.month, now.day)
.subtract(Duration(days: 7))
.toString()
.split(" ")[0]
.toString()
.split("-")
.last,
);
}
I'm a fan of using extensions in dart, and we can use them here like this:
extension DateHelpers on DateTime {
DateTime copyWith({
int? year,
int? month,
int? day,
int? hour,
int? second,
int? millisecond,
int? microsecond,
}) {
return DateTime(
year ?? this.year,
month ?? this.month,
day ?? this.day,
hour ?? this.hour,
second ?? this.second,
millisecond ?? this.millisecond,
microsecond ?? this.microsecond,
);
}
DateTime addYears(int years) {
return copyWith(year: this.year + years);
}
DateTime addMonths(int months) {
return copyWith(month: this.month + months);
}
DateTime addWeeks(int weeks) {
return copyWith(day: this.day + weeks*7);
}
DateTime addDays(int days) {
return copyWith(day: this.day + days);
}
}
You can then use this utility code as follows:
final now = DateTime.now();
final tomorrow = now.addDays(1);
final nextWeek = now.addWeeks(1);
final nextMonth = now.addMonths(1);
final nextYear = now.addYears(1);