The input file is formatted in plain text as an unordered sequence of time-interval descriptions. Each non-empty line describes an interval, which may be simple or periodic, and good or bad. All intervals are bounded by a non-negative start and stop time. Zero as the stop time indicates eternity as the upper bound. The first two columns of the file are start and stop. In the third column, which is optional, is one of six operators: '+' or '-', for simple intervals, or '+g', '+b', '-g', '-b' for periodic intervals. Plus indicates a good interval and minus indicates bad. If not specified, the operator defaults to '+'.
Periodic intervals break each period into two phase-segments, one good and the other bad, both having positive duration. The second character of the operator specifies whether the first segment is the good one or the bad one ('g' or 'b', respectively). The lengths of the first and second segments are the fourth and fifth columns, which are required for periodic intervals. The sum of the two segment lengths is the period, and the stop time is automatically adjusted to the end of whatever period it falls in.
Consistently with the SAS conventions, the time values used to build a good time interval are interpreted as offsets from the XMM-Newton Mission Reference Time (MRT, 1998-01-01T00:00:00.00 TT or 1997-12-31T23:58:56.816 UTC). For convenience it is possible to specify a different reference time with the keyword timeref followed by a time descriptor of the form yyyy-mm-ddThh:mm:ss[.s], as shown in the examples below. Time values are then interpreted as timeref + value - MRT. The time timeref is taken to be expressed in UTC. Not using timeref is equivalent to timeref 1997-12-31T23:58:56.816.
Comments may be placed on empty lines and at the end of non-empty lines, preceded by '#'. Times are given as floating-point numbers. The following examples illustrates each point of syntax.
100 0 # Good time extends from 100 seconds onward,
50 1000 -g 40 20 # punctuated by 20 second bad intervals every
# 60 seconds beginning at 90 seconds.
200 250 - # The instrument had a brief tantrum here.
When using a different timeref:
timeref 2001-12-20T01:02:03 100 0 # Good time extends from timeref + 100s onward
