xTime - A Date/Time Conversion Utility
![[Help]](/Images/Icons/help.gif)
This utility is intended to aid the user in converting times as used
throughout the RXTE, Swift, Fermi, Suzaku, and XMM-Newton 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 time conversions are only valid for times since the
start of the XMM-Newton mission clock (1998-01-01 00:00:00 TT). You may get
incorrect results if you attempt to give inputs before the origins of any of
these respective time systems. It 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. If you
are interested in Fermi mission times as opposed to Swift mission times, make
sure this option is unchecked.
Definitions:
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
- 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
- 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
- Swift/Fermi seconds since 2001.0 UTC (decimal) - e.g., 10676868.604
- Swift/Fermi mission day number, hours, minutes, seconds - e.g., 123:13:47:48.604
- Swift/Fermi decimal mission day - e.g., 123.57487
- Suzaku seconds since 2000.0 UTC (decimal) - e.g., 42299280
- Suzaku mission day number, hours, minutes, seconds - e.g., 489:13:48:00
- Suzaku decimal mission day - e.g., 489.575
- XMM-Newton seconds since 1998.0 TT (decimal) - e.g., 105371344.184
- XMM-Newton mission day number, hours, minutes, seconds - e.g., 1219:13:49:4.184
- XMM-Newton decimal mission day - e.g., 1219.57574287037
Note: The time portion is optional for the following formats: ISO 8601, calendar, year and day number, RXTE mission day number, Swift/Fermi mission day number, Suzaku mission day number, and XMM-Newton 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.
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