MJD We use MJD (Modified Julian Date) to indicate the date in a number of our files. FILE NAMING CONVENTION File names for CGGTTS time transfer files follow the BIPM convention. They are of the form: XFLLmodd.ddd X indicates the GNSS constellation, using the same convention as in the RINEX standard : "G" GPS , "R" for GLONASS (R stands for Russia), "E" for Galileo (Europe), "C" for BeiDou (China), "J" for QZSS (Japan), F indicates the frequencies and number of channels: "S" is for a single-frequency, single-channel observation file "M" is for a single-frequency, multi-channel observation file "Z" is for a dual frequency observation file (always multi-channel) LL is the two alphabetical character code for the laboratory: m is the first character of the receiver identification ["_","0 to 9"] if not applicable or "0 to 9" o is the second character of the receiver identification ["_","0 to 9"] dd.ddd is the MJD of the first observation in the file For example: GZAU0458.932 is dual frequency GPS data from the receiver AU04 on the MJD starting 58932 You can look up the receiver at: https://webtai.bipm.org/database/gnss.html