I want to give the player an item every 5 minecraft days, how would I do that

You could use an event that detects when a player logs onto the game, I cannot remember what event it is though, then add a extended properties file, that has a variable that keeps track the number of tick the player has played, onto them and register then add them to some sort of list in a tick handler and if the number of ticks is less than the number of ticks required, in you case being 24,000 ticks ( refer to this link for conversions: http://minecraft.gamepedia.com/Day-night_cycle), then you increment the number or if then number is greater than or equal to to the number of ticks required then give the player the item and reset their counter. There are some flaws with this system, so you would need to iron those out. This system plan is not perfect, it is just something I came up with on the fly, but I hope that it at least helped you.

Should that only count if the player is online (multiplayer server) or whenever the server is running? (E.g.: Player is offline for 4 days then comes online the 5th day and gets an Item?)

Only when the player is online

Use the PlayerTickEvent to count and IExtendedEntityProperties to store the counter. When the counter reaches a certain value, give the player the Item. Keep in mind that 1 tick = 1/20 seconds.

Can I have some code on how I would do this?

No.

Ok den.

You won't learn anything just by asking for some code. However, I understand how frustrating it can be to just have to bang your head against a wall trying to figure something out.

 

How important is getting this to work, and did you understand what diesieben07 recommended?

You won't learn anything just by asking for some code. However, I understand how frustrating it can be to just have to bang your head against a wall trying to figure something out.

 

How important is getting this to work, and did you understand what diesieben07 recommended?

This is a lootcrate mod, so it is very important I get this working. And yes I do understand what he recommended, I just dont know how I would do it

A summary:

Create a TickHandler (which in this case would be a custom event for OnLivingEvent)

Create an IExtendedProperties Class and register it/add it to a player on constructing

(these two tutorials should help you get an understanding of this Events and IExtendedProperties)

Use the TickHandler to add up a counter inside the ExtendedProperties, use NBT to save the information between saves and loads.

Once the counter reaches your desired value, give item, reset counter.

 

Hopefully this helps get across what everyone was saying, also reread their posts as many times as you need, the answer will come.