Question

I wonder how to compare two DateTime objects in .NET using DateTime methods Compare, CompareTo or Equals without comparing ticks.

I only need a tolerance level of milliseconds or seconds.

How can this be done?

Answer 1

You can subtract one DateTime from another to produce a TimeSpan that represents the time-difference between them. You can then test if the absolute value of this span is within your desired tolerance.

bool dtsWithinASecOfEachOther = d1.Subtract(d2).Duration() <= TimeSpan.FromSeconds(1);

The call to TimeSpan.Duration() can be omitted if you know that the first DateTime cannot represent an earlier point in time than the other, i.e. d1 >= d2.

To answer your query about the comparison methods,
DateTime.Compare(d1, d2) produces the same result as d1.CompareTo(d2):

• 0 if they represent the same point in time (d1.Equals(d2) , d1 == d2). Do note though, that the resolution of DateTime is 1 tick = 100 nanoseconds = 10 ^ -7 seconds.
• A value greater than 0 if d1 is chronologically after d2 (d1 > d2)
• A value less than 0 if d1 is chronologically before d2 (d1 < d2)