It's so rare that, as an adult, one gets ones work handed back so as to have an opportunity to see if one got it right. We do our work, we send it out there.
A few weeks back, a client asked if I could chart Dew Point on a standard graph we produce (showing Temperature and Humidity). I'm pretty sure we can, said I, so I popped over to Wikipedia to find out the pertinent formulae (reasonably complex), added some columns into my spreadsheet to calculate Dew Point, and added the Dew Point to the graphs. I had no idea if they were right at all, I just did the math.
Today, the client and I were talking about the site, and he casually mentioned "I think the software has a checkbox for Dew Point". I checked. Indeed it does. I was too dumb to look.
But the good thing is, I developed this spreadsheet and graph from scratch, and developing my own algorithms. And the result (as seen in the chart) matches the commercially available.
It's nice to get a paper back with a big fat 100% in red ink. Nice to know that I've still got it. At least as far as spreadsheets and math go......