Writing Date/Time Data to a File

User Guide > Working with Date/Time Data > Writing Date/Time Data to a File

There are two methods for writing date/time data to a file. You can use DC_WRITE functions to both convert and write data or you can first convert the date/time data and then write it to a file.

Using DC_WRITE Functions

You can use DC_WRITE functions to convert data from the date/time format to another format and then write the new date/time data to a file. The DC_WRITE functions are easy to use because they automatically handle many aspects of data transfer, such as opening and closing the data file.

The two DC_WRITE functions that you can use to convert and write data are DC_WRITE_FIXED and DC_WRITE_FREE. For examples and a detailed discussion of these two functions, refer to their descriptions in the PV‑WAVE Reference.

note	By default, DC_WRITE_FREE generates CSV (Comma Separated Value) ASCII data files.

Using Conversion Routines

You can also use three conversion routines in conjunction with the WRITE and WRITEU procedures to convert date/time data for output to a file. The conversion routines are:

DT_TO_SEC

DT_TO_STR

DT_TO_VAR

DT_TO_STR Procedure

This procedure converts date/time variables to strings. The procedure has the form:

DT_TO_STR, dt_var

Example

Assume you have a date/time variable named date1 that contains the following date/time structures:

{ 1992 3 13 1 10 34.0000 87474.049 0}

{ 1983 4 20 16 18 30.0000 84224.680 0}

{ 1964 4 24 5 7 25.0000 77289.213 0}

To convert to data, use the DT_TO_STR procedure:

; Convert date/time data. Stores the date data in d and the

; time data in t. The Date_Fmt and Time_Fmt  keywords define

; the formats that date1 is using. DT_TO_STR uses the same

; formats as STR_TO_DT.

; See 
    "STR_TO_DT Function" for an

; explanation of valid formats.

DT_TO_STR, date1, d, t, Date_Fmt=1, Time_Fmt=-1

PRINT, d

; PV-WAVE prints: 03/13/1992 04/20/1983 04/24/1964

PRINT, t

; PV-WAVE prints: 01:10:34 16:18:30 05:07:25

DT_TO_VAR Procedure

This procedure converts date/time variables into variables that contain numerical date/time information. The procedure has the form:

DT_TO_VAR, dt_value

Example

Assume that you have created a date/time variable named date1 that contains the following date/time data:

{ 1992 3 13 10 34 15.0000 87474.440 0}

{ 1983 4 20 12 30 19.0000 84224.521 0}

{ 1964 6 24 16 25 14.0000 77350.684 0}

To convert the data in this date/time variable:

; This procedure creates several variables containing the

; date/time data.

DT_TO_VAR, date1, Year = years, Month = months, Day = days

; The keyword Year generates an integer array that contains

; the years.

PRINT, 'Years =', years

; PV-WAVE prints: Years = 1992 1983 1964

; The keyword Month creates a byte array with the months.

PRINT, 'Months =', months

; PV-WAVE prints: Months = 3 4 6

; The keyword Day creates a byte array with the days of the month.

PRINT, 'Days =', days

; PV-WAVE prints: Days = 13 20 24

DT_TO_SEC Function

This function converts date/time data into seconds. The function has the form:

result = DT_TO_SEC(dt_value)

Example

Assume that you have created the array dtarray that contains the following date/time data:

{ 1992 4 15 7 29 19.0000 87507.312 0}

{ 1993 4 15 7 29 19.0000 87872.312 0}

{ 1994 4 15 7 29 19.0000 88237.312 0}

To find out the number of seconds for each date/time from January 1, 1970, use the DT_TO_SEC function:

seconds = DT_TO_SEC(dtarray, Base = '1-1-70', Date_Fmt = 1)

PRINT, seconds

; PV-WAVE prints: 7.0332296e+08 7.3485896e+08 7.6639496e+08

Version 2017.0