Date calculations

How can I calculate the number of days between two dates?

also...

How can I get the number of days in a given month? (i.e. April would return 30) I would then use this in a calculation.

convert both dates to modified julian dates and subtract.

A ModifiedJulianDate (MJD) is days (and fractions of days) since the start of November 17, 1858.

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