LibreOffice: Turn batch number into date

Here is an example of the batch numbers at my company: 1599. 159 being the day of the YEAR. Day 159 being June 8th (formula needs to account for leap years). The final digit indicates the most recent year ending in that number (9 being 2019). Looking to change the batch number to a (mm/did/yy) format.

Would also like to know how to take that formula and add specific amounts of time for given expirations of products. 18 month expiration and 3 year expiration to be used so I can figure out how to manipulate the formula.

There was a time in college when I could figure this out but I just cannot wrap my head around this problem. Please help me out.

Thank you!

So if the product was made July 8th, 2020 the batch number would be 1590. Our products expire so it is important to know when it was manufactured so we can sell them before expiration.

So far I have gotten the #NAME?

Which part of the equation accounts for the year?

Okay I am getting somewhere.

Referring to A1 as 1599 I used this formula:
=DATE(Year(today()),1,1)+left(a1,3)-1
The “-1” on the end makes up for starting on the 1st of January, 1 day into the year. However, the year will not always be consistent with Today’s year. We have products that were produced in years prior. Maybe an IF function will help? This will be tricky because the final digit referred to the most recent year ending in that number.

@ brett17

Is this what you need?

=DATE(LEFT(YEAR(TODAY()),3)&RIGHT(A1),1,LEFT(A1,3))