| BaseDuration | 
 Base class for date and time durations. 
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| BaseDuration.From | 
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| DatumDependentDuration | 
 DatumDependentDuration represents durations whose length in milliseconds 
 cannot be determined without knowing the datum point. 
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| Duration | 
 Duration represents time periods which have values independent of the context. 
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| TimeCategory | 
 Apply a number of methods to allow convenient Date/Time manipulation,such as: 
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| TimeDatumDependentDuration | 
 TimeDatumDuration represents a time period which results from an
 arithmetic operation between a TimeDuration object and a DatumDuration object 
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| TimeDuration | 
 TimeDuration represents time periods expressed in units of hours, minutes,
 seconds and milliseconds. 
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