1. On 3 March, 2013, I witnessed ....
2. On Thursday, 3 March, 2013, at 4.10 pm, I witnessed ....
3. On 3 March, 2013, at 4.10 pm, I witnessed ....
The year is treated as parenthetical. The comma after the year in a full date is obligatory wherever it stands in a sentence (except at the end, of course).