Rahu kalam - what is this , how to calculate it - explained by Nirban

RAHU KALAM..
inauspicious periods and one should not undertake any 
auspicious work during these periods – especially any 
new undertaking....
Sunday 8th period...
Monday 2nd period..
Tuesday 7th period..
Wednesday 5th period..
Thursday 6th period..
Friday 4th period..
Saturday 3rd period..

But it differs from place to place.. 
because it depends in sunrise and sunset..
and that too differs when place changes..

Now lets calculate Rahu Kalam..
Sunrise in 6:00 AM and sunset 6:00 PM..
calculation is simple..
time difference 12 hours..
12 X 60 = 720 minutes..
720 / 8 = 90 min every part of the day..
1st part = 6:00 AM to 7:30 AM
2nd part = 7:30 AM to 9:00 AM
.....
8th part = 4:30 PM to 6:00 PM

If the day is sunday then 8th part..
i.e. 4:30 PM to 6:00 PM

if the day is tuesday then..
3:00 PM to 4:30 PM

let me know if anyone cannot understand this.