This utility is intended to aid the user in converting times as used throughout the Fermi, LIGO, NuSTAR, RXTE, Suzaku, Swift, XMM-Newton, and Chandra missions between relevant and/or useful time systems and formats. Date/time conversions are also supported for times prior to the RXTE mission, as long as the time systems involved are the same.

Note: RXTE time conversions are only valid for times since the start of the RXTE mission clock (1994-01-01 00:00:00 UTC). Swift/Fermi time conversions are only valid for times since the start of the Swift and Fermi mission clocks (2001-01-01 00:00:00 UTC). Suzaku time conversions are only valid for times since the start of the Suzaku mission clock (2000-01-01 00:00:00 UTC). XMM-Newton/Chandra time conversions are only valid for times since the start of the XMM-Newton/Chandra mission clock (1998-01-01 00:00:00 TT). NuSTAR time conversions are only valid for times since the start of the NuSTAR mission clock (2010-01-01 00:00:00 UTC). LIGO uses the GPS time system for their mission clock, and LIGO/GPS time conversions are only valid for times since the start of the GPS clock (1980-01-06 00:00:00 UTC). You may get incorrect results if you attempt to give inputs before the origins of any of these respective time systems. It also should be noted that Suzaku times are really only accurate to the nearest second.

All raw time stamps in the RXTE and Swift FITS files are given in MET seconds. The file names of RXTE data products are constructed from MET start and stop times using a hexadecimal representation. When the time-related header keywords are properly combined with the time stamp values, the result is TT. For more details, see the RXTE Time Tutorial.

Printed underneath the output table are the clock corrections applicable at that time. For RXTE times, TimeZero is the rough correction that is usually included in the FITS files and that generally guarantees an absolute time accuracy of 0.1 ms. Fine corrections are given separately for PCA and HEXTE. Applying these corrections should improve the absolute time accuracy to about 5 or 8 µs. All corrections are to be added to the time stamps in RXTE FITS files. See also the RXTE Absolute Time Calibration reference. For Swift times, only one correction is applicable: the UT Correction Factor (UTCF). The UTCF is determined from information contained in the clock offset logs created by the Swift MOC following each Malindi pass. For more details see the Guide to Times in Swift FITS Files reference.

Select Apply Clock Offset Correction(s) for RXTE and Swift when converting between mission times and UTC or TT, to have the software account for the offset of the spacecraft clock from civil time automatically. Leap seconds are always included in all applicable conversions (for all missions) regardless of whether the "Apply Clock Correction(s)" box option is enabled. If the input time is outside the range of validity of the available clock offset solution, no clock correction will be shown or applied.

Definitions:

• JD: Julian Date
• MJD: Modified Julian Date = JD - 2,400,000.5
• ISO 8601: YYYY-MM-DD format
• UTC, TT: Coordinated Universal Time, Terrestrial Time
• MET: Mission Elapsed Time

The ISO 8601, calendar date and time, and year and day number formats always use the Gregorian calendar and, depending upon your intended use, may not give valid answers for dates before the Gregorian calendar was adopted.

Usage:

• Enter a date/time in any of the following thirteen formats:
  • IS0 8601 date and time - e.g., 2001-05-04 13:48:00 (or enter "now" for the current date/time)
  • Calendar date and time - e.g., 2001May04 at 13:48:00
  • Year and day number, hours, minutes, seconds - e.g., 2001:124:13:48:00
  • Julian Day (JD) - e.g., 2452034.07500
  • Modified Julian Day (MJD) - e.g., 52033.57500
  • Fermi seconds since 2001.0 UTC (decimal) - e.g., 261135104.544
  • Fermi decimal mission week number - e.g., 45
  • LIGO/GPS seconds since 1980-01-06 00:00:00 UTC (decimal) - e.g., 673019293
  • NuSTAR seconds since 2010.0 UTC (decimal) - e.g., 10676868.604
  • RXTE seconds since 1994.0 UTC (decimal) - e.g., 231601680.622
  • RXTE seconds since 1994.0 UTC (hexadecimal) - e.g., 0xdcdf610
  • RXTE mission day number, hours, minutes, seconds - e.g., 2680:13:48:0.622
  • RXTE decimal mission day - e.g., 2680.57500719408
  • Suzaku seconds since 2000.0 UTC (decimal) - e.g., 42299280
  • Swift seconds since 2001.0 UTC (decimal) - e.g., 10676868.604
  • Swift mission day number, hours, minutes, seconds - e.g., 123:13:47:48.604
  • Swift decimal mission day - e.g., 123.57487
  • XMM/Chandra seconds since 1998.0 TT (decimal) - e.g., 105371344.184
  Note: The time portion is optional for the following formats: ISO 8601, calendar, year and day number, RXTE mission day number, Suzaku mission day number, Swift mission day number, and XMM-Newton/Chandra mission day number. If you do specify a time for one of these formats, the number of seconds is optional.
• Select the appropriate input and output time system for the calendar time formats. You can choose from Terrestrial Time (TT) or Coordinated Universal Time (UTC). Note that the input and output time systems for the mission-specific time formats are always the Mission Elapsed Time (MET) for their respective mission.
• Click on the "Convert" button.