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Posted 19 Jan 2011
Licenced CPOL

Partial DateTime Object Equality

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Determine if specified date/time properrties are equal
While working on a future article, I decided I need to be able to compare two DateTime objects based on any property I chose. In other words, if I wanted to see if two DateTimes objects had the same hour and minute, but didn't care about the rest of the values (year, month, etc) I would need to code it myself. To accomplish this, I wrote a couple of extension methods to satisfy the requirement.

public enum DatePartFlags {Ticks=0, Year=1, Month=2, Day=4, Hour=8, Minute=16, Second=32, Millisecond=64 };
public static class ExtensionMethods
    private static bool FlagIsSet(DatePartFlags flags, DatePartFlags flag)
        bool isSet = ((flags & flag) == flag);
        return isSet;

    public static bool Equal(this DateTime now, DateTime then, DatePartFlags flags)
        bool isEqual = false;
        if (flags == DatePartFlags.Ticks)
            isEqual = (now == then);
            DatePartFlags equalFlags = DatePartFlags.Ticks;
            equalFlags |= (FlagIsSet(flags, DatePartFlags.Year) && now.Year == then.Year) ? DatePartFlags.Year : 0;
            equalFlags |= (FlagIsSet(flags, DatePartFlags.Month) && now.Month == then.Month) ? DatePartFlags.Month : 0;
            equalFlags |= (FlagIsSet(flags, DatePartFlags.Day) && now.Day == then.Day) ? DatePartFlags.Day : 0;
            equalFlags |= (FlagIsSet(flags, DatePartFlags.Hour) && now.Hour == then.Hour) ? DatePartFlags.Hour : 0;
            equalFlags |= (FlagIsSet(flags, DatePartFlags.Minute) && now.Minute == then.Minute) ? DatePartFlags.Minute : 0;
            equalFlags |= (FlagIsSet(flags, DatePartFlags.Second) && now.Second == then.Second) ? DatePartFlags.Second : 0;
            equalFlags |= (FlagIsSet(flags, DatePartFlags.Millisecond) && now.Millisecond == then.Millisecond) ? DatePartFlags.Millisecond : 0;
            isEqual = (flags == equalFlags);
        return isEqual;

Usage is as follows:

private void LoopUntilItHurts()
    DatePartFlags equalityFlags = DatePartFlags.Minute | DatePartFlags.Second;
    DateTime now = DateTime.Now;
    DateTime then = DateTime.Now;
    bool waiting = false;

    while (true)
        now = DateTime.Now;
        if (!waiting)
            int difference = now.Minute % 5;
            then = now.Add(new TimeSpan(0, 0, 1, 0, 0));
            waiting = true;

        if (now.Equal(then, equalityFlags))
            waiting = false;
            // it's time to do something important    
            // sit and spin


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

John Simmons / outlaw programmer
Software Developer (Senior) Paddedwall Software
United States United States
I've been paid as a programmer since 1982 with experience in Pascal, and C++ (both self-taught), and began writing Windows programs in 1991 using Visual C++ and MFC. In the 2nd half of 2007, I started writing C# Windows Forms and ASP.Net applications, and have since done WPF, Silverlight, WCF, web services, and Windows services.

My weakest point is that my moments of clarity are too brief to hold a meaningful conversation that requires more than 30 seconds to complete. Thankfully, grunts of agreement are all that is required to conduct most discussions without committing to any particular belief system.

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Comments and Discussions

Generald'accord! 5+ Pin
Manfred R. Bihy19-Jan-11 9:32
mvpManfred R. Bihy19-Jan-11 9:32 
GeneralReason for my vote of 5 5. Very nice. I may need to hijack ... Pin
Marcus Kramer19-Jan-11 8:14
memberMarcus Kramer19-Jan-11 8:14 

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