user: Question: When has a cause of gas explosion, a Death toll smaller than 63, and a Location of Penygraig?
Columns: ['Colliery', 'Location', 'Date', 'Year', 'Death toll', 'cause']
Types: ['text', 'text', 'text', 'real', 'real', 'text']
Sample row: ['Dinas Colliery', 'Dinas', '1 January', 1844.0, 12.0, 'gas explosion']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "cause" = 'gas explosion' AND "Death toll" < 63.0 AND "Location" = 'Penygraig';