isDaylightTime ( dt )
Returns 1 or 0 to indicate whether the given date falls within U.S. daylight savings time (post-2007)
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Howard Schlossberg - Show more from this author
FM Professional Solutions http://fmprosolutions.com |
Sample input:
isDaylightTime ( date( 5; 1; 2014 ) )
Sample output:
1
Function definition: (Copy & paste into FileMaker's Edit Custom Function window)
Returns 1 or 0 to indicate whether the given date falls within U.S. daylight savings time (post-2007)
Comments
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Scott, Edmonton, AB Apr 29, 2015 |
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| There is a mistake in the DSTEnd calc., it should be identical to the DSTBegin calc except for the month/day values. Instead of simply fixing it that way, I made the following modification dow_oset = floor( mod( 1 + ( yr * 1.25); 7) ); DSTBegin = date( 3 ; 14 ; yr ) - dow_oset; DSTEnd = date( 11 ; 7 ; yr ) - dow_oset An interesting detail to note is DST is a constant at 238 days. Therefore DSTEnd can be obtained thusly: DSTEnd = DSTBegin + 238 Additionally, there is a DayOfWeek function, so the following is equivallent dow_oset = DayOfWeek(date(3, 1, yr)) Here is the entire rewrite: Let([ yr = Year(dt); // DSTBegin is 2nd Sunday of March, minimum is the 8th. FirstPossibleSunday = Date(3; 8; yr); // Offset to 2nd Sunday of March DSTBegin = FirstPossibleSunday + (8 - DayOfWeek(FirstPossibleSunday)) ]; Case( dt < DSTBegin ; 0 ; dt >= DSTBegin + 238 ; 0 ; 1 ) ) |
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Howard Schlossberg, FM Professional Solutions Apr 29, 2015 |
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| Thanks for your notes, Scott. Yours is certainly easier to understand than mine, which I essentially copied from some forum I found online for some other computer language when I needed a solution for whatever I was working on at the time. Meanwhile, I've fixed the missing floor() in my calc above, and visitors now have the option of using mine or yours. Thanks again... |
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