You can use going on before a number to say that something has almost reached that number. For example, you can say that someone is going on 40 to indicate that they are nearly 40.
We've been married for going on two years.
This is 1980 going on 1981.
See full dictionary entry for going
going on in British English
(ˈɡəʊɪŋ ɒn)
preposition
having almost reached (a number)
He's going on 50.
going on two years.
This is 1980 going on 1981.
going on in American English
Informal
nearing or nearly (a specified age or time)
See full dictionary entry for going
Examples of 'going on' in a sentence
going on
He stood by the counter, presumably listening to the heated debate going on within.
Anthony Masters CASCADES - THE DAY OF THE DEAD (2001)
As all the cleaning was going on I'd slipped into a kind of reverie.
Hugo Wilcken THE EXECUTION (2002)
Joaquín must have information that there's a military offensive going on against the guerrillas.
James Grippando A KING'S RANSOM (2001)
All related terms of 'going on'
go on
If you go on doing something, or go on with an activity , you continue to do it.
to be going on with
If you say that something is enough to be going on with , you mean that it is enough for your needs at the moment , although you will need something better at some time in the future .
go back on
If you go back on a promise or agreement , you do not do what you promised or agreed to do.
go down on
To go down on someone means to have oral sex with them.
what sb is (going) on about
If you ask someone what they are on about or what they are going on about , you are puzzled because you cannot understand what they are talking about.