Aging

After fermenting (and distilling, for spirits), most good drinks need time to age. The tool is a wooden barrel — and on the server you must build a proper barrel for this; a plain vanilla Minecraft barrel block will not age brews.
There are two kinds of built barrel. Both are made of wood and registered with a sign — the only real difference is size.
Small barrel
A compact built barrel — still a real structure, just much smaller than the large one.
Build it from 8 wooden stairs in a barrel shape (see the left of the image above).
Place a sign on it and write 
Barrel on any line to register it.
Holds 9 brews.
Large barrel
A big walk-up barrel structure for serious aging.
Build it from 16 wooden stairs, 18 wood planks and 5 fences (the fences form the tap * legs; see the right of the image — it is roughly 4 blocks wide).
Place a sign on it and write 
Barrel on any line to register it.
Holds 27 brews, and once registered you can open it by clicking any of its blocks.
When a barrel is registered you will get a confirmation message in chat. Open it, place your brew inside, close it, and come back later for the aged result.
Wood & time
Wood type matters. Each recipe calls for a specific wood — oak, birch, spruce, dark oak, acacia, and so on — and you get it from the wood you build the barrel out of. The wrong wood changes the outcome, so build a barrel of each wood you brew with.
Aging is measured in "years." On this server, one year is about 20 real minutes or one full in-game day. So a recipe asking for "14 years" needs roughly 4 to 5 hours in the barrel.
Aging happens while you are away and when chunks are not loaded.
Wood types
Every barrel is built from a type of wood, and each recipe calls for a specific one (
Any means it does not matter). When you read a drink's Recipe config block, the 
wood: field is a number — here is the key:
#
Wood
#
Wood
0
Any
7
Crimson
1
Birch
8
Warped
2
Oak
9
Mangrove
3
Jungle
10
Cherry
4
Spruce
11
Bamboo
5
Acacia
12
Cut Copper
6
Dark Oak
13
Pale Oak
A recipe with no 
wood/
age at all (or 
age: 0) needs no barrel — bottle it and drink it straight after fermenting/distilling.