24 lines
1.2 KiB
Text
24 lines
1.2 KiB
Text
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The purpose of this library was to replace our dependence on Unix
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epoch time, which, being limited to a range of about 1970 to 2030,
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is inadequate for our purposes (we have data as old as 1870). This
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date library effectively handles dates from A.D. 1000 to infinity,
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and would probably work all the way back to 0 (ignoring, of course,
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the switch-over to the Gregorian calendar). The useful features of
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Unix epoch time (ease of date difference calculation and date
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comparison, strict ordering) are preserved, and elements such as
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human-legibility are added. The library handles fractional seconds
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and some date/time manipulations used for the Global Positioning
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Satellite system.
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The operators +/-, <=>, cmp, stringify are overloaded. Addition
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handles seconds and fractions of seconds, subtraction handles
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seconds or date differences, compares work, and stringification
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returns the a representation of the date.
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The US Geological Survey (USGS) likes midnight to be 24:00:00 of
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the previous day, not 00:00:00 of the day people expect. If
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$DateTime::Precise::USGSMidnight is set, dprintf will always print
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midnight as 24:00:00 and the date returned from dprintf will have
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the previous day's date. Regardless, time is always stored internally
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as 00:00:00.
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