# Local time to GMT time **URL:** \ **Category:** Shell Programming and Scripting\ **Created:** [February 14, 2017, 11:57am UTC](https://community.unix.com/t/local-time-to-gmt-time/365050 "2017-02-14T11:57:10Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![jiam912](https://community.unix.com/user_avatar/community.unix.com/jiam912/32/2027_2.png) [@jiam912](https://community.unix.com/u/jiam912)\ **Post date:** [February 14, 2017, 11:57am UTC](https://community.unix.com/t/local-time-to-gmt-time/365050/1 "2017-02-14T11:57:10Z")
Gents, Please can help with this. the column in red is the local time the column in blue is the GPStime ```nohighlight 4153152529951 2/12/17 12:00:04.980 951 2960 41531.0 52529.0 1170882022980002 4108153261942 2/12/17 12:00:07.944 942 2959 41081.0 53261.0 1170882025944002 41511523611660 2/12/17 1:55:32.180 1660 2959 41511.0 52361.0 1170888950180002 410675237398 2/12/17 7:36:48.980 98 2958 41067.0 52373.0 1170909426980002 ``` I would like to get the time -3hrs in GMT time. Example ```nohighlight 4153152529951 2/11/17 21:00:04.980 951 2960 41531.0 52529.0 1170882022980002 4108153261942 2/11/17 21:00:07.944 942 2959 41081.0 53261.0 1170882025944002 41511523611660 2/11/17 22:55:32.180 1660 2959 41511.0 52361.0 1170888950180002 410675237398 2/12/17 04:36:48.980 98 2958 41067.0 52373.0 1170909426980002 ``` Please advise. Thanks for your help ---
**Author:** ![Corona688](https://community.unix.com/letter_avatar/corona688/32/5_5575768a8748004e209b776fc1b2916d.png) [@Corona688](https://community.unix.com/u/Corona688)\ **Post date:** [February 14, 2017, 12:10pm UTC](https://community.unix.com/t/local-time-to-gmt-time/365050/2 "2017-02-14T12:10:17Z")
By 'column' I think you mean 'row'. What's your system? Date math is tricky without GNU date. ---
**Author:** ![jiam912](https://community.unix.com/user_avatar/community.unix.com/jiam912/32/2027_2.png) [@jiam912](https://community.unix.com/u/jiam912)\ **Post date:** [February 14, 2017, 12:13pm UTC](https://community.unix.com/t/local-time-to-gmt-time/365050/3 "2017-02-14T12:13:29Z")
Dear Corona688 sorry there was a error in the color, it is column, 🙂 i am using debian 7. i try to do it manually (hr-3) but i belive it can be done automatically, maybe using the GPStime? ---
**Author:** ![Corona688](https://community.unix.com/letter_avatar/corona688/32/5_5575768a8748004e209b776fc1b2916d.png) [@Corona688](https://community.unix.com/u/Corona688)\ **Post date:** [February 14, 2017, 1:12pm UTC](https://community.unix.com/t/local-time-to-gmt-time/365050/4 "2017-02-14T13:12:54Z")
But ... that column doesn't change. And the row you highlighted before still changes. What does 1170882025944002 represent, anyway? ---
**Author:** ![vgersh99](https://community.unix.com/user_avatar/community.unix.com/vgersh99/32/14851_2.png) [@vgersh99](https://community.unix.com/u/vgersh99)\ **Post date:** [February 14, 2017, 1:13pm UTC](https://community.unix.com/t/local-time-to-gmt-time/365050/5 "2017-02-14T13:13:39Z")
something to start with to see the conversion ONLY: `awk -f jiam.awk myInputFile` where `jiam.awk` is: ```nohighlight { d=$2 t=$3 split(d,dA,"/") split(t,tA,"[:.]") dateSpec=sprintf("20%02d %02d %02d %02d %02d %02d", dA[3], dA[1], dA[3], tA[1], tA[2], tA[3]) time=mktime(dateSpec) utc=strftime("%m/%d/%Y %H:%M:%S." tA[4], time, 1) printf("dateSpec->[%s] utc->[%s]\n", dateSpec, utc) } ``` ---
**Author:** ![RudiC](https://community.unix.com/letter_avatar/rudic/32/5_5575768a8748004e209b776fc1b2916d.png) [@RudiC](https://community.unix.com/u/RudiC)\ **Post date:** [February 14, 2017, 2:07pm UTC](https://community.unix.com/t/local-time-to-gmt-time/365050/6 "2017-02-14T14:07:23Z")
Mayhap sth. along this line: ```plaintext awk -vGPS0=$(TZ=UTC date -d'1/6/1980 0:00' +%s) '{print "@" int($NF/1E6)+GPS0}' CONVFMT="%.f" file | LC_ALL=C TZ=+3 date -f- Sat Feb 11 21:00:23 2017 Sat Feb 11 21:00:26 2017 Sat Feb 11 22:55:50 2017 Sun Feb 12 04:37:07 2017 ``` > [@corona688](#): > > . > . > . > What does 1170882025944002 represent, anyway? That's the GPS date / time representation, starting at 6. Jan 1980, 0:00h UTC, in microseconds. Delta to \*nix epoch is 315964800 sec. ---
**Author:** ![Chubler\_XL](https://community.unix.com/user_avatar/community.unix.com/chubler_xl/32/2077_2.png) [@Chubler\_XL](https://community.unix.com/u/Chubler_XL)\ **Post date:** [February 14, 2017, 3:31pm UTC](https://community.unix.com/t/local-time-to-gmt-time/365050/7 "2017-02-14T15:31:31Z")
jiam912, you seem to work with gpstime in your data files a fair bit. perhaps you would benefit from this GNU awk function strfgps() which operates like the strftime() function except with gpstime: ```nohighlight TZ=0 gawk ' function strfgps(fmt, gps) { gsub(/%f/, sprintf("%03d", gps % 1E6 / 1E3), fmt) return strftime(fmt, gps / 1E6 + 315964800) } { $2 = strfgps("%m/%d/%y", $NF) $3 = strfgps("%H:%M:%S.%f", $NF) print }' OFS="\t" infile ``` I used gsub() to add support for the `%f` format =\> milliseconds as 3 digit number. output: ```nohighlight 4153152529951 02/11/17 21:00:22.980 951 2960 41531.0 52529.0 1170882022980002 4108153261942 02/11/17 21:00:25.944 942 2959 41081.0 53261.0 1170882025944002 41511523611660 02/11/17 22:55:50.180 1660 2959 41511.0 52361.0 1170888950180002 410675237398 02/12/17 04:37:06.980 98 2958 41067.0 52373.0 1170909426980002 ``` ---
**Author:** ![jiam912](https://community.unix.com/user_avatar/community.unix.com/jiam912/32/2027_2.png) [@jiam912](https://community.unix.com/u/jiam912)\ **Post date:** [February 15, 2017, 5:48am UTC](https://community.unix.com/t/local-time-to-gmt-time/365050/8 "2017-02-15T05:48:08Z")
Dear Xl and all thanks a lot ---------- Post updated at 05:48 AM ---------- Previous update was at 12:38 AM ---------- Dear Xl I have added ```nohighlight return strftime(fmt, gps / 1E6 + 315964800 - 18) ``` To get exactly the time -3hs