When you're talking about how long something has been going on, it's common to talk about "round" numbers like one year, five years, 6 months, ten days, two hours, etc. When the time that's passed has almost reached one of those round numbers, but not quite, use "nearly":

We've been married for nearly ten years.

This one is nearly a month old, believe it or not.

I've lived here for nearly 15 years, off and on.

"Nearly" is very similar to "almost", and they can be used interchangeably in most situations.