An Easy Mnemonic to Format Dates As Strings in C#

I originally posted this post on my blog.

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Is it MM or mm for months when formatting dates? Is it "yyyy-MM-dd" or "yyyy-mm-dd"?

I always forgot which one to use...Until I figured out an easy mnemonic.

MM vs mm

Ask yourself: Which one represents a larger time frame? Months or minutes?

Since one month is larger than one minute, it's M for months. An uppercase m is larger than a lowercase m.

Write, anyDate.ToString("yyyy-MM-dd").

mm vs fff

Then, what is it for milliseconds? Isn't it mm?

Now, ask yourself: Which one is faster? One minute or one millisecond?

Since one millisecond is faster, write f.

Write anyTime.ToString("hh:mm:ss.fff").

Easy, peasy now!

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Comments

[Baltasar García Perez-Schofield]

Good point.

Alas, I can't understand how date/time objects don't include a toShortIso() or something like that, producing the data in yyyy-MM-dd/hh:mm:ss formats.

[Cesar Aguirre]

You're right! The closest methods are ToLongDateString and ToShortDateString...or something like that.