Item on the map

When exactly does items appear on the map, is there a specific time or anything like that, is it really rare for them to pop up

im asking this purely because I don’t wanna miss anything item wise on the map thank you 

If there isn't an event currently in progress that drops specific items, you'll find map finds after each 'New Day' (00:05 TCT). These drops do scale with activity and the more active you are, the more likely you are to find something, however there's no need to keep checking all day. 

im asking this purely because I don’t wanna miss anything item wise on the map

Once items are on the map, they are there forever. They do not disappear.

I always check a little after  the new day starts 12am TCT
I believe they will stack if you don't check it daily but from what I understand new stuff won't appear if you don't do an action each day. 
I check my daily out of habit.

also don't get your hopes up if you don't get anything for days or even a week, the RNG is super low. I would also advise against putting merits into it. Better to use those for EDU starting out

Each Torn day, there is a chance for something to spawn on the map.

Your base chance can be increased through working in certain companies like a Zoo, putting merits into Awareness, and reading a book that increases Awareness. 

The items will not despawn so you could wait a year, then pick everything up in one go.

The only requirement to trigger items to spawn is to be active within 24 hours of the Torn day. 

I do check occasionally but I haven’t found a thing, I saw that someone found a parachute and I haven’t found a thing, wondering if I find anything at this rate 

RNG

It blesses and curses in the same second. You can have max Awareness and be in Awareness Awareness Week and still find nothing good. 

Also, just having more Awareness doesn't necessarily increase the quality of the items. It merely increases your chance of having something spawn on the map.

Adding on to the above comments:

During events items may also spawn randomly throughout the day when the map is checked

You're 1 day old....have patience....there'll be a lot of useless junk for you to pick up in the coming days, weeks, months, years...

Higher levels of activity do not increase chances of something spawning. As long as you're active in the past 24 hours something has the chance to spawn

Source

I got goodies bag in the mapLoad image: love_chemistry