Is there a better way to trim a DateTime to a specific precision?

Question

What's the best way to trim a DateTime object to a specific precision? For instance, if I have a DateTime with a value of '2008-09-29 09:41:43', but I only want it's precision to be to the minute, is there any better way to do it than this?

private static DateTime TrimDateToMinute(DateTime date)
{
    return new DateTime(
        date.Year, 
        date.Month, 
        date.Day, 
        date.Hour, 
        date.Minute, 
        0);
}

What I would really want is to make it variable so that I could set its precision to the second, minute, hour, or day.

score 117 · Accepted Answer · edited Feb 16 '18 at 04:57

117

static class Program
{
    //using extension method:
    static DateTime Trim(this DateTime date, long roundTicks)
    {
        return new DateTime(date.Ticks - date.Ticks % roundTicks, date.Kind);
    }

    //sample usage:
    static void Main(string[] args)
    {
        Console.WriteLine(DateTime.Now);
        Console.WriteLine(DateTime.Now.Trim(TimeSpan.TicksPerDay));
        Console.WriteLine(DateTime.Now.Trim(TimeSpan.TicksPerHour));
        Console.WriteLine(DateTime.Now.Trim(TimeSpan.TicksPerMillisecond));
        Console.WriteLine(DateTime.Now.Trim(TimeSpan.TicksPerMinute));
        Console.WriteLine(DateTime.Now.Trim(TimeSpan.TicksPerSecond));
        Console.ReadLine();
    }

}

edited Feb 16 '18 at 04:57

Zach Saw

4,308
3
33
49

answered Sep 30 '08 at 13:26

Bartek Szabat

2,904
1
20
13

I like this very much and if I was using the 3.5 framework, this is the route I would take, unless there's something better still out there. Unfortunately, I'm using 2.0 so I'll have to stick to your first answer. Thanks! – Lloyd Cotten Sep 30 '08 at 13:48
18

If you're making it a general-purpose extension method, it's worth preserving the DateTimeKind (Unspecified/Utc/Local): return new DateTime(date.Ticks - date.Ticks % roundTicks, date.Kind); – Joe Oct 03 '08 at 11:12
... or a one-liner that also preserves the Kind property: d = d.AddTicks(-(d.Ticks + 30*TimeSpan.TicksPerSecond) % TimeSpan.TicksPerMinute); – Joe Oct 04 '08 at 06:55
@Joe thanks man, I came here to write the same comment after spending 2 hours debugging expired auth tokens :)) – Alex from Jitbit Mar 20 '20 at 22:05

score 9 · Answer 2 · edited May 14 '15 at 16:47

9

You could use an enumeration

public enum DateTimePrecision
{
  Hour, Minute, Second
}

public static DateTime TrimDate(DateTime date, DateTimePrecision precision)
{
  switch (precision)
  {
    case DateTimePrecision.Hour:
      return new DateTime(date.Year, date.Month, date.Day, date.Hour, 0, 0);
    case DateTimePrecision.Minute:
      return new DateTime(date.Year, date.Month, date.Day, date.Hour, date.Minute, 0);
    case DateTimePrecision.Second:
      return new DateTime(date.Year, date.Month, date.Day, date.Hour, date.Minute, date.Second);
    default:
      break;
  }
}

and expand as required.

edited May 14 '15 at 16:47

Jeff B

8,572
17
61
140

answered Sep 30 '08 at 12:25

Rikalous

4,514
1
40
52

For Hour and Minute, I'm wondering if Minutes and Seconds should be rounded than using 0? – Vivek Sep 30 '08 at 13:33
2

Certainly you could adapt the code to round rather than truncate should you need to; often I find truncation feels more natural as that is effectively how clocks behave. – Rikalous Sep 30 '08 at 14:38
when you need it only once - return new DateTime(dt.Year, 1, 1) – Baglay Vyacheslav Oct 08 '18 at 14:08
Please remember to preserve the `DateTime.Kind`. – BrainSlugs83 Jun 04 '21 at 23:02

rocketsarefast · Answer 3 · 2019-08-06T17:33:35.243

8

I like this method. Someone mentioned it was good to preserve the Date Kind, etc. This accomplishes that because you dont have to make a new DateTime. The DateTime is properly cloned from the original DateTime and it simply subtracts the remainder ticks.

public static DateTime FloorTime(DateTime dt, TimeSpan interval) 
{
  return dt.AddTicks(-1 * (dt.Ticks % interval.Ticks));
}

usage:

dt = FloorTime(dt, TimeSpan.FromMinutes(5)); // floor to the nearest 5min interval
dt = FloorTime(dt, TimeSpan.FromSeconds(1)); // floor to the nearest second
dt = FloorTime(dt, TimeSpan.FromDays(1));    // floor to the nearest day

edited Aug 06 '19 at 17:33

answered Apr 01 '13 at 20:17

rocketsarefast

4,072
1
24
18

Since DateTime format is a structure (value type), any manipulation will create a new value even though it does not present it that way. https://stackoverflow.com/a/1859266/955444 – bkqc Jul 09 '19 at 14:23
True, but it is properly cloned by the DateTime code, so the time zone is indeed preserved. I will slightly reword my answer to be more clear. Thank you. – rocketsarefast Jul 13 '19 at 18:56

Marcos Arruda · Answer 4 · 2017-04-26T15:25:22.980

1

There are some good solutions presented here, but when I need to do this, I simply do:

DateTime truncDate;
truncDate = date.Date; // trim to day
truncDate = date.Date + TimeSpan.Parse(string.Format("{0:HH:00:00}", date)); // trim to hour
truncDate = date.Date + TimeSpan.Parse(string.Format("{0:HH:mm}", date)); // trim to minute
truncDate = date.Date + TimeSpan.Parse(string.Format("{0:HH:mm:ss}", date)); // trim to second

Hope it helps.

edited Apr 26 '17 at 15:25

answered Nov 07 '14 at 18:30

Marcos Arruda

532
7
15

doesn't work, returns only the day + 00:00:00 – Kᴀτᴢ Apr 26 '17 at 11:45
@katz: I'm sorry, but I tested this solution when I published my reply and I have just tested it again and it works perfectly fine. Are you sure you're not testing only the first option above (trim to day)? I don't believe that all the TimeSpan.Parse method calls above are returning to you 00:00:00. Are you sure you're using a DIFFERENT variable (other than the variable "date" itself) to receive the results of these operations (as I used "truncDate" in my example)? If you use the "date" variable itself, the first operation above will truncate it to day, compromising all other results below. – Marcos Arruda Apr 26 '17 at 15:08
@katz: Use a DIFFERENT variable (like "truncDate") and don't do ALL the operations above in sequence and THEN print the result. My code was just an example, but EACH operation (each code line) should be used separately, depending on the precision you want (day, hour, minute or second). For instance, try to execute only the LAST line (trim to second) and then print the result. – Marcos Arruda Apr 26 '17 at 15:12
@katz: Sorry, in the "trim to hour" code line, the was an error, and I have just edited the code. It seems the string format "{0:HH}" does not return (as I would expect) the hour component of the date,so I changed it to "{0:HH:00:00}, which works fine. The other code lines are correct. And all the observations I made in the comments above are still valid. – Marcos Arruda Apr 26 '17 at 15:29
Thanks for your support. With the changes everything is working :) +1 – Kᴀτᴢ Apr 27 '17 at 06:46

score -2 · Answer 5 · answered Jun 01 '12 at 10:49

-2

DateTime dt = new DateTime()
dt = dt.AddSeconds(-dt.Second)

Above code will trim seconds.

answered Jun 01 '12 at 10:49

Gunarathinam

436
1
5
14

It will not trim milliseconds and will result in bad `dt`. – Denis Jan 03 '14 at 12:11
1

Just add .AddMillisceconds() too then. This answer is suprerior to the other ones in my opinion, since it is way less boiler plate. But please correct me. – PuerNoctis Aug 01 '19 at 05:54

Is there a better way to trim a DateTime to a specific precision?

5 Answers5

Linked