When the instrument sends a packet to the telemetry it will always contain a time stamp. This timestamp is derived from the spacecraft clock pulse. The resolution of the spacecraft clock is 2^-16 seconds. (= 15 microsec.) In the WFC's, however, the highest used resolution is 2^-12 (1/4096) seconds. The time resolutions are: DIR001 Normal mode 2^-11 = 488 microsec. DIR002 High Time Resolution mode 2^-12 = 244 microsec. DIR003 Background Analysis mode 2^-10 = 977 microsec. DIR004 Diagnostic Reduced mode 2^-12 = 244 microsec. DIR005 Diagnostic Extended mode 2^-12 = 244 microsec. All other modes have a time resolution of 1 second only. In the FITS files produced by Stage-I times can occur as keyworods in headers and as columns in the rows of the data part. As a general rule in Stage-I all times of the eventfiles are the clock times in 2^-12 ticks. This does not reflect the actual time resolution. All times in the headers are in MJD