This command applies to timeseries where data are composed of dates/times. It has no meaning unless the command `set xdata time` is given also.
Syntax:
set timefmt "<format string>"
show timefmt
The string argument tells `gnuplot` how to read timedata from the datafile. The valid formats are:
Format Explanation
%d day of the month, 1--31
%m month of the year, 1--12
%y year, 0--99
%Y year, 4-digit
%j day of the year, 1--365
%H hour, 0--24
%M minute, 0--60
%s seconds since the Unix epoch (1970-01-01, 00:00 UTC)
%S second, 0--60
%b three-character abbreviation of the name of the month
%B name of the month
Any character is allowed in the string, but must match exactly. \t (tab) is recognized. Backslash-octals (\nnn) are converted to char. If there is no separating character between the time/date elements, then %d, %m, %y, %H, %M and %S read two digits each, %Y reads four digits and %j reads three digits. %b requires three characters, and %B requires as many as it needs.
Spaces are treated slightly differently. A space in the string stands for zero or more whitespace characters in the file. That is, "%H %M" can be used to read "1220" and "12 20" as well as "12 20".
Each set of non-blank characters in the timedata counts as one column in the `using n:n` specification. Thus `11:11 25/12/76 21.0` consists of three columns. To avoid confusion, `gnuplot` requires that you provide a complete using specification if your file contains timedata.
Since `gnuplot` cannot read non-numerical text, if the date format includes the day or month in words, the format string must exclude this text. But it can still be printed with the "%a", "%A", "%b", or "%B" specifier: see `set format` for more details about these and other options for printing timedata. (`gnuplot` will determine the proper month and weekday from the numerical values.)
See also xdata and `Time/date` for more information.
Example:
set timefmt "%d/%m/%Y\t%H:%M"
tells `gnuplot` to read date and time separated by tab. (But look closely at your data—what began as a tab may have been converted to spaces somewhere along the line; the format string must match what is actually in the file.) See also time data demo.