MS_TIME(3)

DESCRIPTION
Time conversion and string generation

SYNOPSIS
#include <libmseed.h>
MS_EPOCH2HPTIME(X) X * (hptime_t) HPTMODULUS
MS_HPTIME2EPOCH(X) X / HPTMODULUS
hptime_t ms_btime2hptime ( BTime *btime );
char    *ms_btime2isotimestr ( BTime *btime, char *isotimestr );
char    *ms_btime2mdtimestr ( BTime *btime, char *mdtimestr );
char    *ms_btime2seedtimestr ( BTime *btime, char *seedtimestr );
int      ms_hptime2btime ( hptime_t hptime, BTime *btime );
char    *ms_hptime2isotimestr ( hptime_t hptime, char *isotimestr,
                                flag subseconds );
char    *ms_hptime2mdtimestr ( hptime_t hptime, char *mdtimestr,
                               flag subseconds );
char    *ms_hptime2seedtimestr ( hptime_t hptime, char *seedtimestr,
                                 flag subseconds );
hptime_t ms_time2hptime ( int year, int day, int hour, int min,
                          int sec, int usec );
hptime_t ms_seedtimestr2hptime ( char *seedtimestr );
hptime_t ms_timestr2hptime ( char *timestr );

DESCRIPTION
These routines convert between various time formats. Internally, libmseed represents time values as high precision epoch times (hptime), the number of ticks from the epoch: 00:00:00.00 1 January 1970. By default a tick is defined as a microsecond (0.000001 seconds). See INTERNAL HPTIME below for more details. Also used is the SEED binary time represented by the following data structure (defined in libmseed.h):

typedef struct btime_s
{
  uint16_t  year;     /* year with century                 */
  uint16_t  day;      /* day, 1 - 366                      */
  uint8_t   hour;     /* hour, 0 - 23                      */
  uint8_t   min;      /* minute, 0 - 59                    */
  uint8_t   sec;      /* second, 0 - 60 (60 = leap second) */
  uint8_t   unused;   /* unused alignment byte             */
  uint16_t  fract;    /* fractional seconds, 0 - 9999      */
} BTime;
MS_EPOCH2HPTIME is a macro which converts a Unix/POSIX epoch time (elapsed seconds since 1 January 1970) to a hptime which are related by a simple scaling factor. MS_HPTIME2EPOCH is a macro which converts an hptime to a Unix/POSIX epoch time (elapsed seconds since 1 January 1970) which are related by a simple scaling factor. The result can be cast to an integer, in which cast no rounding is performed and sub-second precision is truncated, or can be cast into a double to get a double precision epoch time. ms_btime2hptime converts a btime to a hptime. ms_btime2isotimestr generates an ISO recommended format time string from a btime. Example: '2001-07-29T12:38:00.0000'. The isotimestr must have enough room for 25 characters. The resulting string will be NULL terminated. ms_btime2mdtimestr generates a month-day formatted time string from a btime. Example: '2001-07-29 12:38:00.0000'. The mdtimestr must have enough room for 25 characters. The resulting string will be NULL terminated. ms_btime2seedtimestr generates a SEED format time string from a btime. Example: '2001,195,12:38:00.0000'. The seedtimestr must have enough room for 23 characters. The resulting string will be NULL terminated. ms_hptime2btime converts a hptime to a btime. By default, hptime has microsecond precision whereas a BTime structure can only represent time to 0.0001 seconds. The precision will be lost during this conversion, it will not be accounted for by rounding but will be truncated. This behavior is by design. ms_hptime2isotimestr generates an ISO recommended format time string from a hptime. Example: '2001-07-29T12:38:00.000000' or '2001-07-29T12:38:00'. The isotimestr must have enough room for 27 characters. The subseconds flag controls whether the sub-second precision is included or not. The resulting string will be NULL terminated. ms_hptime2mdtimestr generates a month-day formatted time string from a hptime. Example: '2001-07-29 12:38:00.000000' or '2001-07-29 12:38:00'. The isotimestr must have enough room for 27 characters. The subseconds flag controls whether the sub-second precision is included or not. The resulting string will be NULL terminated. ms_hptime2seedtimestr generates a SEED format time string from a hptime. Example: '2001,195,12:38:00.000000' or '2001,195,12:38:00'. The seedtimestr must have enough room for 25 characters. The subseconds flag controls whether the sub-second precision is included or not. The resulting string will be NULL terminated. ms_time2hptime converts the time represented by the specified year, day, hour, min, sec and usec (microseconds) to an hptime. The range expected for each value is as follows:

year : 1900 - 2100
day  : 1 - 366  (366 = last day of leap year)
hour : 0 - 23
min  : 0 - 59
sec  : 0 - 60   (60 = leap second)
usec : 0 - 999999
ms_seedtimestr2hptime converts a SEED time string to a hptime. The time format expected is: "YYYY[,DDD,HH,MM,SS.FFFFFF]", the delimiter can be a comma [,], colon [:] or period [.] except for the fractional seconds ("FFFFFF") which must begin with a period [.] if present. ms_timestr2hptime converts a time string to a hptime. The time format expected is: "YYYY[/MM/DD HH:MM:SS.FFFFFF]", the delimiter can be a dash [-], slash [/], colon [:], or period [.] and between the date and time a [T] or a space may be used. The fractional seconds ("FFFFFF") must begin with a period [.] if present. For both ms_seedtimestr2hptime and ms_timestr2hptime the input time string may be "short", in which case the vales omitted on the right hand side are assumed to be 0 (with the exception of month and day which are assumed to be 1). The year is always required.

RETURN VALUES
ms_btime2hptime, ms_time2hptime, ms_seedtimestr2hptime and ms_timestr2hptime return a hptime on success and HPTERROR on error. ms_btime2isotimestr, ms_btime2mdtimestr, ms_btime2seedtimestr, ms_hptime2isotimestr, ms_hptime2mdtimestr and ms_hptime2seedtimestr return a pointer to the resulting string or NULL on error. ms_hptime2btime returns 0 on success and -1 on error.

INTERNAL HPTIME
The time values internal to libmseed are defined as the number of ticks from the epoch: 00:00:00.00 1 January 1970 and often referred to as hptime. By default a tick is defined as a microsecond (0.000001 seconds). The tick interval, and thus hptime precision, is controlled by the definition of HPTMODULUS in libmseed.h. It is not recommended to change HPTMODULUS from the default value of 1000000. This epoch time system is similar to the Unix/POSIX epoch times except that the ticks are higher precision than the 1-second ticks used in POSIX. An hptime can always be converted to a Unix/POSIX epoch time by dividing hptime by HPTMODULUS (reducing the hptime to second precision) and vise-versa, see the documentation for the MS_HPTIME2EPOCH and MS_EPOCH2HPTIME macros above. As long as the system's gmtime function supports negative epoch times the internal time routines will be able to represent times earlier than the epoch, i.e. times earlier than 1 January 1970. The hptime values are stored as 64-bit integers to allow high precision and avoid accumulation errors associated with floating point values. A special value defined as HPTERROR in libmseed.h is used to represent errors for routines returning hptime.

AUTHOR
Chad Trabant
IRIS Data Management Center