SEC_TO_DT Function

Reference Guide > S Routines > SEC_TO_DT Function

SEC_TO_DT Function

Converts any number of seconds into date/time values.

Usage

result = SEC_TO_DT(num_of_seconds)

Input Parameters

num_of_seconds—A scalar representing the number of seconds elapsed from the date specified in the system variable !DT_Base.

Returned Value

result—A date/time variable containing the converted values.

Keywords

Base—A string containing a date, such as “3-27-92”. This is the base date from which the number of seconds is calculated. The default value for Base is taken from the system variable !DT_Base.

Date_Fmt—Specifies the format of the base date, if passed into the function. Possible values are 1, 2, 3, 4, or 5, as summarized in Date Format.

Table 16-1: Date Format
Value	Format Description	Examples for May 1, 1992
1	MMDD[YY]YY	05/01/92
2	DDMM[YY]YY	01-05-92
3	ddd*[YY]YY	122,1992
4	DDmmm[mmmmmm][YY]YY	01/May/92
5	[YY]YYMMDD	1992-05-01

where the asterisk (*) represents one of the following separators: dash (–), slash (/), comma (,), period (.), or colon (:).

For a description of these formats, see the PV‑WAVE User’s Guide.

Discussion

This function is useful for converting time stamps that count seconds to date/time values. Most time stamps count seconds from an arbitrary base date. For example, the UNIX time stamp counts seconds from January 1, 1970.

Example 1

This example shows how a value of 20 seconds is represented internally inside a date/time variable after it has been converted with SEC_TO_DT. The example uses a base start date of January 1, 1970.

date = SEC_TO_DT(20, Base='1-1-70', Date_Fmt=1)

PRINT, date

; PV-WAVE prints: { 1970 1 1 0 0 20.0000 79367.000 0}

Example 2

Assume you have the following dataset which contains time stamps and associated measurements. The file contains data collected from January 1, 1990 to January 5, 1990. The base date for the clock is January 1, 1970.

6.3119520e+08   113

6.3128160e+08   768

6.3136800e+08   632

6.3145440e+08   227

6.3154080e+08   224

Assume the above file has been read into two variables. The first column is read into a double-precision array called tarray. The second column is read into an array called fluid_level, which indicates the water level of a lake for each specified time period. You can convert the date/time data in Column 1 to date/time data with the SEC_TO_DT function:

dtarray = SEC_TO_DT(tarray, Base='1-1-70')

PRINT, dtarray

; PV-WAVE prints:

; { 1990   1   1  12   0  1.01192e-05   86672.500   0}

; { 1990   1   2  12   0  1.01192e-05   86673.500   0}

; { 1990   1   3  12   0  1.01192e-05   86674.500   0}

; { 1990   1   4  12   0  1.01192e-05   86675.500   0}

; { 1990   1   5  12   0  1.01192e-05   86676.500   0}

Notice the SEC_TO_DT function creates an array containing a date/time structure for each of the seconds values. The Julian day shown for each date/time is automatically adjusted to reflect the system base date of September 14, 1752.