This source says 1914:

https://www.grangeracademic.com/results.asp?inline=true&image=0354231&wwwflag=4&itemx=1&screenwidth=408

Which makes sense as they looks like mostly older soldiers.

So it’s a toss if this is pre or post WW1 being declared. Judging by the smile of 4th from the left and the last guy, I’d say this is after war got declared.

I’m struck by how modern those bicycles look

Are we not trusting the text on the picture? It says June 1916