There are details of the screen dates for The Passion over on its website now -- see Episode Guide:
Episode 1: Sunday 16 March, 8pm-9pm, BBC1
Episode 2: Monday 17 March, 8.30pm-9pm, BBC1
Episode 3: Saturday 22 March, TBA, BBC1
Episode 4: Sunday 23 March, TBA, BBC1
The times of each episode are not yet announced on the site, but a glance at the Radio Times gives the timings for the first two episodes, and I have added those above.