In mathematics, the symbol `≤` can mean between.

`a ≤ x ≤ d` -- `x` must between `a` and `d` possibly including either `a` or `d`

So... `≤ 2014` perhaps

However, for general purposes I don't think using `<` or `-` is a problem. 

Heck you could possibly consider a tilde, `~`. Tilde means "approximately".