A TimeFrame represents a moment in time as either an Modified Julian Date (MJD), a Julian Date (JD), a Besselian epoch or a Julian epoch, as determined by the System attribute. Optionally, a zero point can be specified (using attribute TimeOrigin) which results in the TimeFrame representing time offsets from the specified zero point.
Even though JD and MJD are defined as being in units of days, the TimeFrame class allows other units to be used (via the Unit attribute) on the basis of simple scalings (60 seconds = 1 minute, 60 minutes = 1 hour, 24 hours = 1 day, 365.25 days = 1 year). Likewise, Julian epochs can be described in units other than the usual years. Besselian epoch are always represented in units of (tropical) years.
The TimeScale attribute allows the time scale to be specified (that is, the physical
process used to define the rate of flow of time). MJD, JD and Julian epoch can be used
to represent a time in any supported time scale. However, Besselian epoch may only be
used with the
" (Terrestrial Time) time scale. The list of supported time scales
includes universal time and siderial time. Strictly, these represent angles rather than
time scales, but are included in the list since they are in common use and are often
thought of as time scales.
When a time value is formatted it can be formated either as a simple floating point value, or as a Gregorian date (see the Format attribute).
AlignTimeScale: Time scale in which to align TimeFrames
LTOffset: The offset of Local Time from UTC, in hours.
TimeOrigin: The zero point for TimeFrame axis values
TimeScale: The timescale used by the TimeFrame
Several of the Frame attributes inherited by the TimeFrame class refer to a specific
axis of the Frame (for instance Unit(axis), Label(axis), etc). Since a TimeFrame is
strictly one-dimensional, it allows these attributes to be specified without an axis
index. So for instance,
" is allowed in place of
astCurrentTime: Return the current system time