Time zone data for Dhaka is missing an end date

nikolaus_brauer at us.ibm.com nikolaus_brauer at us.ibm.com
Thu Jul 9 22:54:09 UTC 2009

To whom it may concern,

I am writing to report an issue I have discovered in the recent change to 
the Asia/Dhaka time zone data, which recently implemented daylight saving 
time in June. The recent update to the time zone data (tzdata2009j) 
includes a start date for daylight saving time, but no end date. 
Intuitively, daylight saving time should have a start and an end date 
within the same year, otherwise what is implemented is an indefinite GMT 
offset change. Because of this programs that detect DST rules may see the 
absence of an end to the DST period as an error. This may cause programs 
which obtain DST rules using Olson time zone data to fail to detect 
daylight saving time rules for Asia/Dhaka. For completeness, I propose a 
tentative end date be implemented now, and an updated date be implemented 
once an official date is released, or the government releases an 
additional tentative date in September. 

According to timeanddate.com:

        "The press secretary did not confirm the length of DST but stated 
that the government would decide the DST end date and would announce it 
later. On another note, Bangladesh's minister for power said earlier in 
2009 that the new timing might          continue until the end of 
September. Timeanddate.com will provide an update on the DST end date when 
it becomes available. "


Timeanddate.com picked September 25th, which seems like a likely enough 
date. I have update the tzdata on my system with the following rules to 
implement this change.

# Rule  NAME    FROM    TO      TYPE    IN      ON      AT      SAVE 
Rule    Dhaka09 2009    max     -       Jun     19      23:00   1:00    D
Rule    Dhaka09 2009    max     -       Sep     26      00:00   0:00    S  

# Zone  NAME            GMTOFF  RULES   FORMAT  [UNTIL]
Zone    Asia/Dhaka      6:01:40 -       LMT     1890
                        5:53:20 -       HMT     1941 Oct    # Howrah Mean 
                        6:30    -       BURT    1942 May 15 # Burma Time
                        5:30    -       IST     1942 Sep
                        6:30    -       BURT    1951 Sep 30
                        6:00    -       DACT    1971 Mar 26 # Dacca Time
                        6:00    Dhaka09 B%sT                # Bangladesh 

Could you please evaluate this change for inclusion in the Olson time zone 
data? Please let me know if you have any questions or concerns. 


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