NSA Time
NSA time corresponds with earth time, such as books like Narnia. Narnian time and earth time intersect, but are random in span. Not so with NSA. A NSA year is one quarter of a School year. This does make the forth year longer (because it includes not just the last school quarter, but also summer, think of it like a leap year).
So to get NSA years from Earth years:
([current Earth year] - 1998 ) * 4 = Rounded NSA years
from NSA to Earth is:
[NSA years] divided by 4 + 1998 = Rounded Earth time
Because NSA was founded in 1998, it is the base value added or subtracted.
Further information
Rounded Time: These are only full Earth years, or NSA years that are multiples of four. This is when you can use the above equations without further complication.
At my time editing this post it is 2023 earth time, on August 14. This means that (2023 - 1998) * 4 = 100. BUT, public schools in the US just started the first school year quarter (I am writing this while procrastinating on Dual Credit Statistics), this means that a new NSA year has started, so, it is in fact nsaY 101.
nsaY: NSA year [insert year here]