How can I format and round the DateTime.Now to the nearest time on the pc time up or down ?

Question

How can I format and round the DateTime.Now to the nearest time on the pc time up or down ?

sharon glipman 441

public void Test()
        {
            var datetime = DateTime.Now;
            var res = RoundUp(datetime, TimeSpan.FromMinutes(5));
        }

        DateTime RoundUp(DateTime dt, TimeSpan d)
        {
            return new DateTime((dt.Ticks + d.Ticks - 1) / d.Ticks * d.Ticks, dt.Kind);
        }

No matter what is the time I want to round it up or download depending to what it's closet.

For example if the time is 13:51 then round it to 1350 if it's 1353 round to 1355 the goal is to round it to 0 or 5 depending to what the minutes in the are clos to.
If to 0 or to 5

For example the time is 16:31 then format and round it to 1630 but if the time is 19:47 then format it to 1945 and if it's 11:29 to 1130 or if its 10:01 round it to 1000

The round should be to 0 or 5 in the minutes third digit I don't need the seconds only for the rounding maybe.

18:33 will be 1835

What I'm trying to archive my goals :

Format the DateTime.Now from example the current time and format is : {14/10/2021 14:28:45} then format it to : 202110141428 without the seoconds
Round the formatted time up or download depending to what is more close on the minutes to 0 or 5

So if for example the time and format is now : {14/10/2021 14:28:45} after format and rounding it should be : 202110141430 because 28 is close to 30 the minute 8 is closer to the 0 so it will be 30 and if it was {14/10/2021 14:26:45} then the result will be : 202110141425

I think the method RoundUp is working for the rounding but only up not sure if this is 100% what I need but it's close to my goal. I need also RoundUp and to format the time.

Update :

I see now that if the time is 14:45 for example the roundup will change the minutes to 14:50 but if it's 14:45 I want to keep it that way to move it up by 5 minutes but to correct it to the nearest 5 minutes needed if it's 14:45 leave it 45 but if it's 14:46 change it back to 14:45 but if it's closer to the 50 like 14:48 change it to 14:50 and if it's 14:43 change it to 14:45 if it's 14:42 change it to 14:40

This is the logic it should be by rounding up/down

Accepted answer

1 additional answer

Your answer

Answer 1

P a u l 10,761

I believe the issue is that you're dividing by d.Ticks, which will truncate (throw away) the decimal place of the result, then you're multiplying by d.Ticks, which means you're always flooring to the nearest 5 minute interval, rather than rounding.

You first need to cast d.Ticks to a float/double so the division becomes a floating point division, and the decimal portion of the result is retained. You then have a multiple of "5 minutes" expressed as a fraction, which you can then round using Math.Round to round it up or down (whichever's nearest), and then lastly multiply that by d.Ticks to get the final result.

Hopefully that's what you're explaining in your question - I verified it using some of your expected outcomes:

class Program {
    static void Main(string[] args) {
        var tests = new (DateTime Input, string Output)[] {
            (new DateTime(2021, 10, 14, 13, 51, 00), "14/10/2021 13:50:00"),
            (new DateTime(2021, 10, 14, 13, 53, 00), "14/10/2021 13:55:00"),
            (new DateTime(2021, 10, 14, 16, 31, 00), "14/10/2021 16:30:00"),
            (new DateTime(2021, 10, 14, 19, 47, 00), "14/10/2021 19:45:00"),
            (new DateTime(2021, 10, 14, 11, 29, 00), "14/10/2021 11:30:00"),
            (new DateTime(2021, 10, 14, 10, 01, 00), "14/10/2021 10:00:00"),
            (new DateTime(2021, 10, 14, 18, 35, 00), "14/10/2021 18:35:00")
        };

        DateTime Round(DateTime date, TimeSpan interval) {
            return new DateTime(
                (long)Math.Round(date.Ticks / (double)interval.Ticks) * interval.Ticks
            );
        }

        var interval = TimeSpan.FromMinutes(5);

        foreach (var (Input, Output) in tests) {
            var actual = Round(Input, interval).ToString();
            var expected = Output;

            Console.WriteLine($"Actual: {actual}, Expected: {expected}, Pass: {actual == expected}");
        }
    }
}

sharon glipman 441 Reputation points

2021-10-14T15:30:11.087+00:00

In the results it's showing the same on the left and right. How can I show on the left the test date time and on the left the result

The result is :

The Actual and the Expected are the same :

How can I display on the left side the time and date before the changes ?

To show in the same format like in the right side but the date and time before the changes : 2021, 10, 14, 13, 51, 00 and 2021, 10, 14, 13, 53, 00
To show those as actual.
P a u l 10,761 Reputation points

2021-10-14T16:22:20.357+00:00
You can just include Input:

Console.WriteLine($"Input: {Input}, Actual: {actual}, Expected: {expected}, Pass: {actual == expected}");

sharon glipman 441

Last question please. It's working but what if I want to generate amount of random date times ?

I'm using this method to generate random :

public IEnumerable<DateTime> GenerateRandomDates(int numberOfDates)
        {
            var rnd = new Random(Guid.NewGuid().GetHashCode());

            for (int i = 0; i < numberOfDates; i++)
            {
                var year = rnd.Next(1, 10000);
                var month = rnd.Next(1, 13);
                var days = rnd.Next(1, DateTime.DaysInMonth(year, month) + 1);

                yield return new DateTime(year, month, days,
                    rnd.Next(0, 24), rnd.Next(0, 60), rnd.Next(0, 60), rnd.Next(0, 1000));
            }
        }

For example 100 and it's generating 100 dates times.
But I'm not sure if it's the same format you are using and how to use it with your code ? but what I'm trying to archive is a method that I can give a number and it will generate random date times and then using it with your code.

P a u l 10,761 Reputation points

2021-10-14T17:04:15.387+00:00
Well the meat of the snippet I included is:

DateTime Round(DateTime date, TimeSpan interval) { return new DateTime( (long)Math.Round(date.Ticks / (double)interval.Ticks) * interval.Ticks ); }

In the part of your code that calls GenerateRandomDates you could generate a specific time interval (TimeSpan.FromMinutes(5); like in the original example.) Then pass each DateTime into Round:

var interval = TimeSpan.FromMinutes(5); foreach (var date in GenerateRandomDates()) { Console.WriteLine(Round(date, interval)); }

This means you'll end up with 100 DateTimes that are all rounded to the nearest 5 minutes.
sharon glipman 441 Reputation points

2021-10-14T17:15:19.947+00:00
Great. Last thing I try to archive in my original question is to Format the DateTime.Now from example the current time and format is : {14/10/2021 14:28:45} then format it to : 202110141428 without the seconds.

To convert the date time to long int in the format like I show : Year , month , days , hours , minutes but as long int not date time.

var interval = TimeSpan.FromMinutes(5); foreach (var date in GenerateRandomDates(100)) { datestimes.Add(Round(date, interval)); }

datestimes is List<DateTime>

After creating the List or while creating the List to create also another List of long int with the random timedates but as long int's.

Can I create a List<long> ?
P a u l 10,761 Reputation points

2021-10-14T17:34:04.77+00:00
You can format a DateTime to that format like this:

var dt = new DateTime(2021, 10, 14, 13, 51, 00); var formattedDate = dt.ToString("yyyyMMddHHmmss"); Console.WriteLine(formattedDate);

You can then parse that out into a long (omitted error handling here for brevity):

var lngDate = long.Parse(formattedDate); Console.WriteLine(lngDate);

I'm not sure if there's much point converting it to a numerical data type unless there's arithmetic you were planning on doing to that number, but that's how you can do it.
sharon glipman 441 Reputation points

2021-10-14T17:53:16.847+00:00

The reason I want to convert it is because I have this link :

https://mysite.com/Radar_202110141415.gif

The number in the end is date with time in the format I want. this link is updating every 5 minutes the next one for example will be :

https://mysite.com/Radar_202110141420.gif then
https://mysite.com/Radar_202110141425.gif

This is why I wanted first to round it and now I want to format it to this number format so I can build the future link/s
P a u l 10,761 Reputation points

2021-10-14T18:00:23.72+00:00

Sure, in that case you can just use formattedDate instead of lngDate from my previous example. If it's just a suffix for a filename then it can stay as a string.
sharon glipman 441 Reputation points

2021-10-14T18:00:37.227+00:00

The result after formatting and converting to long is not the format I need :

The original date time : {08/02/0922 9:35:00}

After converting it to long : 9220208093643

And it should be after the cconversion 092202080935 like this Radar_202110141415
P a u l 10,761 Reputation points

2021-10-14T18:10:46.723+00:00
If you use this instead:

var formattedDate = dt.ToString("yyyyMMddHHmm");

It should give you what you want. Numerical types won't display leading zeros when they're printed (in the case of the year 0922) so you should stick with the string formattedDate instead.
sharon glipman 441 Reputation points

2021-10-14T18:48:26.963+00:00
Now that I checked again the links how can I change the method Round so if the current time on the pc is 5 or 0 don't round it but anything else if not 5 or 0 round it down. always down. for example 14:22 round to 14:20 or 15:59 down to 15:55 round time only direction and to another variable to the method like int timestoround and make a for loop so it will keep round down from the current datetime.now for example 23 times so in the end I will get a List for example of : 14:25 , 14:20 , 14:15 , 14:10......23 times down.

Sorry for the mess. I found that I need only round down and specific number of times.

DateTime Round(DateTime date, TimeSpan interval) { return new DateTime( (long)Math.Round(date.Ticks / (double)interval.Ticks) * interval.Ticks ); }

P a u l 10,761

You can just use Math.Floor instead:

DateTime RoundDown(DateTime date, TimeSpan interval) {
    return new DateTime(
        (long)Math.Floor(date.Ticks / (double)interval.Ticks) * interval.Ticks
    );
}

sharon glipman 441 Reputation points

2021-10-14T19:08:38.373+00:00
and how do I make it to round down 23 times ? or any number of times ?

for (int i = 0; i < 23; i++) { var dt = RoundDown(DateTime.Now, TimeSpan.FromMinutes(5)); datestimes.Add(dt); }

datestimes is List<DateTime>

The problem is that it will add to the List each time the same round down.

I want that it will round down once the current DateTime.Now and then fro mthat point to add to the list more 22 round down dates times.

The first one for example is 14:50 so the rest 22 should be 14:45 , 14:40 , 14:35.......23 times

P a u l 10,761

Something like this should do it:

var dates = new List<DateTime>();
var current = Round(DateTime.Now, TimeSpan.FromMinutes(5));

for (var i = 0; i < 23; i++) {
    dates.Add(current);

    current = current.AddMinutes(-5);
}

Stuart 1 Reputation point

2022-01-26T18:21:06.583+00:00
There is a bug with the rounding implementation for certain values of interval due to double precision that will result in incorrect rounding.

The following is a fix that doesn't involve type conversion

public static DateTime RoundDown(DateTime timestamp, TimeSpan interval) { var residual = timestamp.Ticks % interval.Ticks; return new DateTime(timestamp.Ticks - residual); }

Answer 2

Use modulus in the custom rounding equation. Keep in mind, this rounds to minutes. Seconds are not used which is how I understand your requirements.

static void Main(string[] args)  
{  
    const int nearestMinutes = 5;  
    const int roundUpLimit = 3;  
  
    DateTime dt = new DateTime(2021, 10, 14, 10, 3, 0);  
    int remainder = dt.Minute % nearestMinutes;  
    int roundUp = nearestMinutes - remainder;  
  
    DateTime newDt;  
    if(remainder >= roundUpLimit)  
    {  
        newDt = new DateTime(dt.Year, dt.Month, dt.Day, dt.Hour, dt.Minute + roundUp, 0);  
    }  
    else  
    {  
        newDt = new DateTime(dt.Year, dt.Month, dt.Day, dt.Hour, dt.Minute - remainder, 0);  
    }  
  
    Console.WriteLine(newDt.ToString());  
}

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How can I format and round the DateTime.Now to the nearest time on the pc time up or down ?

1 additional answer

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