Table: fahed_attal_match_details
Columns: date
venue
score
result
competition

Question: What date has a competition of 2012 afc challenge cup, and dasarath rangasala stadium, kathmandu as the venue?
SQL: SELECT "date" FROM fahed_attal_match_details WHERE "competition" = '2012 afc challenge cup' AND "venue" = 'dasarath rangasala stadium, kathmandu'