In France, when gathered with friends, it is customary to drink beers or other light alcohol around 7pm, and this time is called apéritif (or apéro). Does this custom have an English (UK and/or US) equivalent? How would you say "on se verra à l'apéro"?
The term cocktail hour has been used in the US to mean
the interval before the evening meal during which cocktails and other alcoholic beverages are often served
However, this is not limited to beer and light alcoholic beverages, but may include wine or strong spirits as well.
Some places have "happy hour", where a bar serves slightly cheaper drinks in the early evening.
There's a whole load of vernacular expressions for going to the pub and having a drink, but they're not really associated with a time: "go for a pint", "swift half", etc.
The apéro is a French phenomenon, a particularly pleasant one --especially when combined with ti' punch-- but as already pointed out there is no equivalent term for it in English because the custom itself does not exist.
The closest translation I can think of is tea. In Britain and the British world, you can meet for tea which means something to eat and, well, tea. The exact time varies from place to place and according to social background (see the link above) but come over for tea will be understood in the British world as come over this afternoon for a light snack and a drink.
As a native English speaker living in the south of France I must stress again that this does not have the same connotations as the French apéro. For example, alcohol may well be absent if you meet for tea while it most certainly will be present if you meet for apéro. Still tea is the closest you'll find in English.
EDIT: Coctail hour is indeed closer despite this being the accepted answer.
I think the closest equivalent has another French word:
Hors d'oeuvre which is also called Appetizers
It is more food related, but is close to your situation as in
Can we meet for appetizers?
That said, I (Danish) would certainly understand what you meant if you asked me to join you for an apéritif
In spite of what is being said, I believe that "Happy Hour," traditionally after high tea (4pm) and before the evening meal (supper/dinner around 7 or 8pm) is a common tradition where not only are drinks cheaper in order for the establishment to attract a larger clientele in this off-hour, but often nibbles or little bite-sized food and appropriately small plates are provided gratis. Both provided by private or commercial establishments to boost their off-hours with the hopes of providing the local cafe or hotel restaurant with an evening's crowd and happy returning customers.