FINA recently posted the Swimming order of events for the 2012 Olympics, including estimated timelines for when each event will start. 

The competition dates for Swimming are July 28-August 4, 2012; prelims  sessions begin at 10:00 a.m.; finals at 7:30 p.m. 

That posting can be found on the FINA website here:
http://www.fina.org/H2O/index.php?option=com_content&view=article&id=2683&Itemid=1246

Finals event order is 
as follows (final, unless noted as semi-final):

DAY 1: SATURDAY JULY 28, 2012
Men's 400 IM
Women's 100 fly (semi-final)
Men's 400 free
Women's 400 IM
Men's 100 breaststroke (semi-final)
Women's 400 Free Relay

DAY 2: SUNDAY JULY 29, 2012
Women's 100 fly
Men's 200 free (semi-final)
Women's 100 breaststroke (semi-final)
Men's 100 breaststroke
Women's 400 free
Men's 100 back (semi-final)
Women's 100 back (semi-final)
Men's 400 Free Relay

DAY 3: MONDAY JULY 30, 2012
Women's 200 free (semi-final)
Men's 200 free
Women's 100 back
Men's 100 back
Women's 100 breaststroke
Men's 200 fly (semi-final)
Women's 200 IM (semi-final)

DAY 4: TUESDAY JULY 31, 2012
Men's 100 free (semi-final)
Women's 200 free
Men's 200 fly
Women's 200 fly (semi-final)
Men's 200 breaststroke (semi-final)
Women's 200 IM
Men's 800 Free Relay

DAY 5: WEDNESDAY AUGUST 1, 2012
Men's 200 breaststroke
Women's 100 free (semi-final)
Men's 200 back (semi-final)
Women's 200 fly
Men's 100 free
Women's 200 breaststroke (semi-final)
Men's 200 IM (semi-final)
Women's 800 Free Relay

DAY 6: THURSDAY AUGUST 2, 2012
Men's 50 free (semi-final)
Women's 200 breaststroke
Men's 200 back
Women's 200 back (semi-final)
Men's 200 IM
Women's 100 free
Men's 100 fly (semi-final)

DAY 7: FRIDAY AUGUST 3, 2012
Women's 200 back
Men's 100 fly
Women's 800 free
Men's 50 free
Women's 50 free (semi-final)

DAY 8: SATURDAY AUGUST 4, 2012
Women's 50 free
Men's 1500 free
Women's 400 Medley Relay
Men's 400 Medley Relay