Do SAS datasets have a timezone attribute for datetimes?

[rbetancourt]

I'm trying to get the hang of working with SAS timezones.  Bottom of Page 42,  SAS NLS: Reference, 5th Ed. states:

"When you specify a time zone, SAS adds a time-zone-specific timestamp to data sets and SAS catalogs when the data set or catalog is created or modified".

The following calls the datetime() and  tzones2u() functions, which are influenced by the timezone option in effect:

NOTE: This session is executing on the X64_10PRO  platform.

1          %let dt_fmt = dateampm.;
2          
3          options tz='America/New_York';
4          data ny;
5             ny_dt     = datetime();
6             ny_2_utc  = tzones2u(ny_dt);
7             *ny_tz_off = cat(put(tzoneoff(ny_dt) / 3600, 8.), ':00');
8          run;

NOTE: The data set WORK.NY has 1 observations and 2 variables.     

9          
10         options tz='Asia/Shanghai';
11         data sha;
12            sha_dt    = datetime();
13            sha_2_utc = tzones2u(sha_dt);
14            *sha_tz_off = cat(put(tzoneoff(sha_dt) / 3600, 8.), ':00');;
15         run;

NOTE: The data set WORK.SHA has 1 observations and 2 variables.

16         
17         options tz='America/New_York';
18         data both;
19            merge ny
20                  sha;
21         diff = intck('hour', ny_dt, sha_dt, 'Continuous');
22         
23         put 'New York Datetime:      ' ny_dt     &dt_fmt  /
24         	'New York 2 UTC:         ' ny_2_utc  &dt_fmt //
25             'Shanghai Datetime:      ' sha_dt    &dt_fmt  /
26             'Shanghai 2 UTC:         ' sha_2_utc &dt_fmt //
27         'Time Difference NY and SHA: ' diff ' Hours';
28         run;

New York Datetime:      04FEB19:02:10:23 PM
New York 2 UTC:         04FEB19:07:10:23 PM

Shanghai Datetime:      05FEB19:03:10:23 AM
Shanghai 2 UTC:         04FEB19:07:10:23 PM

Time Difference NY and SHA: 13  Hours

29         
30         proc contents data = ny;run;
31         proc contents data = sha;run;

NOTE: SAS Institute Inc., SAS Campus Drive, Cary, NC USA 27513-2414

The output from PROC CONTENTS does not appear to display such an attribute.

                                      The CONTENTS Procedure

           Data Set Name        WORK.NY                       Observations          1 
           Member Type          DATA                          Variables             2 
           Engine               V9                            Indexes               0 
           Created              02/04/2019 14:10:23           Observation Length    16
           Last Modified        02/04/2019 14:10:23           Deleted Observations  0 
           Protection                                         Compressed            NO
           Data Set Type                                      Sorted                NO
           Label                                                                      
           Data Representation  WINDOWS_64                                            
           Encoding             wlatin1  Western (Windows)                            


                                Engine/Host Dependent Information

Data Set Page Size          65536                                                                 
Number of Data Set Pages    1                                                                     
First Data Page             1                                                                     
Max Obs per Page            4062                                                                  
Obs in First Data Page      1                                                                     
Number of Data Set Repairs  0                                                                     
ExtendObsCounter            YES                                                                   
Filename                    C:\Users\randy\AppData\Local\Temp\SAS Temporary                       
                            Files\_TD9972_RANDY-PC_\ny.sas7bdat                                   
Release Created             9.0401M5                                                              
Host Created                X64_10PRO                                                             
Owner Name                  randy-PC\randy                                                        
File Size                   128KB                                                                 
File Size (bytes)           131072                                                                


                            Alphabetic List of Variables and Attributes
 
                                   #    Variable    Type    Len

                                   2    ny_2_utc    Num       8
                                   1    ny_dt       Num       8


                                      The CONTENTS Procedure

           Data Set Name        WORK.SHA                      Observations          1 
           Member Type          DATA                          Variables             2 
           Engine               V9                            Indexes               0 
           Created              02/04/2019 14:10:23           Observation Length    16
           Last Modified        02/04/2019 14:10:23           Deleted Observations  0 
           Protection                                         Compressed            NO
           Data Set Type                                      Sorted                NO
           Label                                                                      
           Data Representation  WINDOWS_64                                            
           Encoding             wlatin1  Western (Windows)                            


                                Engine/Host Dependent Information

Data Set Page Size          65536                                                                 
Number of Data Set Pages    1                                                                     
First Data Page             1                                                                     
Max Obs per Page            4062                                                                  
Obs in First Data Page      1                                                                     
Number of Data Set Repairs  0                                                                     
ExtendObsCounter            YES                                                                   
Filename                    C:\Users\randy\AppData\Local\Temp\SAS Temporary                       
                            Files\_TD9972_RANDY-PC_\sha.sas7bdat                                  
Release Created             9.0401M5                                                              
Host Created                X64_10PRO                                                             
Owner Name                  randy-PC\randy                                                        
File Size                   128KB                                                                 
File Size (bytes)           131072                                                                


                           Alphabetic List of Variables and Attributes
 
                                  #    Variable     Type    Len

                                  2    sha_2_utc    Num       8
                                  1    sha_dt       Num       8

If someone supplies a dataset with datetime values created with a SAS instance where the timezone in effect is unknown, then how would I convert the incoming datatimes to a timezone other than the timezone in effect in this current instance of SAS.

Thanks in advance,

Randy

[PGStats]

I think the dataset timestamp is UTC and reported by proc contents according to your locale, as demonstrated by:

options tz='America/New_York';
data ny;
Hello = "World";
run;

proc contents data = ny; run;

options tz='Asia/Shanghai';
proc contents data = ny; run;

                               The CONTENTS Procedure

    Data Set Name        WORK.NY                       Observations          1
    Member Type          DATA                          Variables             1
    Engine               V9                            Indexes               0
    Created              2019-02-04 17:01:13           Observation Length    5
    Last Modified        2019-02-04 17:01:13           Deleted Observations  0
.
.
.
                               The CONTENTS Procedure

    Data Set Name        WORK.NY                       Observations          1
    Member Type          DATA                          Variables             1
    Engine               V9                            Indexes               0
    Created              2019-02-05 06:01:13           Observation Length    5
    Last Modified        2019-02-05 06:01:13           Deleted Observations  0
...

[rbetancourt]

Thanks to both @PGStats and @ChrisNZ  for the helpful responses.  And I verified it with:

4  options tz='America/New_York';
5  data both;
6     merge ny
7           sha;
8  diff = intck('hour', ny_dt, sha_dt, 'Continuous');
9
10  sha_tzone_off_now = cat(put(tzoneoff(sha_dt) / 3600, 8.), ':00');
11
12  put 'New York Datetime:      ' ny_dt     &dt_fmt  /
13      'New York 2 UTC:         ' ny_2_utc  &dt_fmt //
14      'Shanghai Datetime:      ' sha_dt    &dt_fmt  /
15      'Sha TZ offset then:     ' sha_tz_off_then    /
16      'Sha TZ offset now:      ' sha_tz_off_then    //
17      'Shanghai 2 UTC:         ' sha_2_utc &dt_fmt /
18  'Time Difference NY and SHA: ' diff ' Hours';
19  run;

New York Datetime:      04FEB19:05:16:44 PM
New York 2 UTC:         04FEB19:10:16:44 PM

Shanghai Datetime:      05FEB19:06:16:44 AM
Sha TZ offset then:     8:00
Sha TZ offset now:      8:00

Shanghai 2 UTC:         04FEB19:10:16:44 PM
Time Difference NY and SHA: 13  Hours

[ChrisNZ]

I reported this documentation error. 

The value is shifted.  No “time-zone-specific timestamp” is “added”.

[ChrisNZ]

Good news. The documentation is being revised.

From:

When you specify a time zone, SAS adds a time-zone-specific timestamp to data sets and SAS catalogs when the data set or catalog is created or modified. 

The time-zone-specific timestamp is also added to the SAS log when SAS starts and to the output at execution.

To:

When you specify a time zone, SAS shifts the datetime value according to the time zone and stores the new value.

The time-zone-specific timestamp is displayed to the SAS log.

[rbetancourt]

@ChrisNZ, thank you for the follow-up!

[ChrisNZ · Accepted solution]

Very interesting question.

I think there is not flag or "stamp" or attribute set or added anywhere. So this can be a misread:

"When you specify a time zone, SAS adds a time-zone-specific timestamp to data sets and SAS catalogs when the data set or catalog is created or modified".

What happens as far as I understand is that if time zones are known in the SAS session, SAS uses that information to shift the datetime values. This shift takes place both when storing values (as you have shown) and when retrieving them (as @PGStats showed).