I finally had Covid. I was traveling for work at the end of October, and I came back with it. But I'd had my shots, and I managed to make it nearly three years into this ordeal before finally getting it. Apparently being a mostly shut-in has its perks. I got the weird smell/taste thing, and the lingering cough but otherwise it was mostly no big deal except for the mental fog. I tend to be a rather analytical person, so not being able to think at all came as a shock, I had three days where I just couldn't do much of anything.

For my job I wear three primary hats: sysadmin, DBA, and analyst. We are a manufacturing company, and I handle our product attribution, including assigning GTIN identifiers to products. GTINs are Global Trade Identification Numbers, they are typically 14 digit unique identifiers assigned by GS1 and other trusted quasi-governmental entities. While GS1 has made it fairly simple to create GTINs ad hoc as needed, sometimes we will be working on a project where I need to add a lot. Fortunately there is an import from CSV template function that allows for mass import, the trick is that I have to assign each GTIN manually. The GTIN is made up of a reference to the packaging level, followed by the company Global Location Number (GLN), then incremental digits, followed by a check digit. All of this is easy to assign manually, except the check digit which requires some logic.

=MOD(-SUM(MID(A1&0,{1,3,5,7,9,11,13;2,4,6,8,10,12,14},1)*{3;1}),10)

The Excel formula above returns the check digit value, given a 13 digit string of the packaging level, GLN, and incremental digits. Change the cell reference A1 to whatever cell for the source 13 digit string. I can't take credit for this formula, I found it somewhere years ago when I was first creating GTINs for all of our products. It is very handy as it lets me figure out GTIN values to then use in the import template.