Many functions in the ChartDirector API accept dates/times
as parameters, in which the dates/times are represented as the seconds elapsed
since 1-1-0001 00:00:00.
ChartDirector provides a function phpchartdir.chartTime that returns a
ChartDirector date/time (seconds elapsed since 1-1-0001 00:00:00) given the
year, month, day, hour, minute and second components of a date.
A common date/time format used in some systems is to represent dates/times as seconds
elapsed since 1-1-1970 00:00:00 GMT in 32-bit integers. ChartDirector does not use
this time format because it cannot represent dates before the year 1970, which may be
necessary for charting applications. Instead, ChartDirector provides a function
phpchartdir.chartTime2 for converting this time format to ChartDirector's date/time format.