Get the Month and Year X number of months from now

Question

I am attempting to generate a PageView that will display the Month and Year related to the number of times you swipe in either directon.

Example 1:

I swipe right twice, so I get Feb 2021

Example 2:

I swipe left 12 times, so I get April 2020

I have attempted to create a DateTime.now() and subtract an integer of months, but I'm not having much luck. I have looked at various plugins like DateUtils, but again no luck.

I have been at what should be a simple solution for while now and would appreciate a guidance.

The closet I get is the following which requires me to know the days in each month which isn't ideal

(DateTime.now().subtract(Duration(days: 90)).toString())

Huthaifa Muayyad · Accepted Answer · 2021-04-03T07:39:22.200

1

From DataTime docunamtion:

Returns a new [DateTime] instance with [duration] added to [this].

var today = DateTime.now();

var fiftyDaysFromNow = today.add(const Duration(days: 50));

// adds 1 days

DateTime _future = DateTime.now().add(const Duration(days: 1));

//substracts 1 day
DateTime _tomorrow2 = DateTime.now().subtract(const Duration(days: 1));

Also this, credit ,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

edited Apr 03 '21 at 07:39

answered Apr 03 '21 at 07:36

Huthaifa Muayyad

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Thanks, but I need to increment or decrement by months, not days. – Yonkee Apr 03 '21 at 07:39
check my modified answer :) – Huthaifa Muayyad Apr 03 '21 at 07:39
You're most welcome, kindly consider marking at we an answer if it solved your question :) – Huthaifa Muayyad Apr 03 '21 at 07:44
Blindly incrementing or decrementing `date.month` won't work if `date.day` isn't valid for that month. – jamesdlin Apr 03 '21 at 08:00
He's not interested in days, but month and year. Also, days can be accounted for easily. Scope of the question was how to subtract months besides using i increments of 30 – Huthaifa Muayyad Apr 03 '21 at 08:17
And this breaks down if we're looking at the 30th or 31st day of the month. See my video at "Proper Month and Day Arithmetic in Dart and Flutter: https://youtu.be/LpoBYgzKVwU" for details. – Randal Schwartz Apr 04 '21 at 00:07

Randal Schwartz · Answer 2 · 2021-04-04T00:09:07.210

Y'all are going about it wrong. Presuming 24 hours in a day, or 30 days in a month, is just wrong. Here's how to always get midnight the first of the month, 7 months before today:

void main() {
  var n = DateTime.now();
  print(DateTime(n.year, n.month - 7, 1));
}

Just use DateTime constructors. They wrap around just fine. Works at month's end as well:

void main() {
  var n = DateTime(2021, 2, 28);
  print(DateTime(n.year, n.month, n.day + 1));
  n = DateTime(2020, 2, 28);
  print(DateTime(n.year, n.month, n.day + 1));
}

Which correctly shows 3/1 for 2021, and 2/29 for 2020, as it was a leap year.

Stop adding 24-hour days! I've got a video that explains why.... https://www.youtube.com/watch?v=usFSVUEadyo

And here's a video that goes into this with more detail: Proper Month and Day Arithmetic in Dart and Flutter: youtu.be/LpoBYgzKVwU

And here's a video that goes into this with more detail: Proper Month and Day Arithmetic in Dart and Flutter: https://youtu.be/LpoBYgzKVwU — Randal Schwartz, Apr 04 '21 at 00:05

Get the Month and Year X number of months from now

2 Answers2