When can a GC holder apply for Citizenship?

[vinaysandela]

Question for Parents. They are on GreenCard and want to check on when can they apply for Citizenship?
Are there are any specific days to count? Can we get any from anywhere to see that information?

Thanks

[newacct]

Take the "resident since" date on their green card, count forwards by 5 years, then backwards by 90 days. That's the earliest they can file N-400 under the 5-year rule (assuming they have not interrupted continuous residence during that time).