Planet	Duration in Each Rashi
Sun	1 month
Moon	2 days
Mars	1 month 15 days
Mercury	1 month

Jupiter	1 year
Venus	1 month
Saturn	2 years and 6 months
Rahu, Ketu	1 year and 6 months

It is evident from the above table that  Sun stays in Each rashi for 1 month and so on.