Bangladesh does not currently operate Daylight-Saving Time.
In 2009, there was a brief period when DST was implemented, to address electricity shortages. According to a Daily Star newspaper report at the end of 2009, it was announced that clocks would go back one hour on 31 December and then move forward one hour on 31 March the following year, 2010. (See www.thedailystar.net)
Then, on 22 March 2010 The Daily Star reported that the Bangladesh Cabinet cancelled Daylight Saving Time.
"The cabinet on Monday permanently cancelled the Daylight Saving Time system considering sufferings and difficulties of different sections of professionals and people."
The international dialling code for Bangladesh is +880.