When I first saw somebody using k instead of zero in a banner to write the year, I got thrilled because it looked geeky. Years later, now the same thing gets me irritated. For one thing, the practice started probably by some tech event had spread across all the colleges like a virus, affected all events that had nothing to do with tech and math, essentially becoming a cliche. For another, it is meaningless.
We use letters instead of 1000 and its multiples since it saves space. Writing 1M is better than putting a one followed by six zeros. In the case of years, this is applicable to the ones like 2000. That's why it makes sense to write Y2K Problem (even if your original intention was to get a geeky look). Doing the same for an year like 2018 has no advantages (except the cliche geeky look, yes). But why don't you just write 0.2018 × 104 then?
People who still don't count notations like 2k18 a cliche may ask, "but what is wrong with it?" Make your mind blank, and now you'll read 2k18 like:
- 200018, since 2k18 seems to be a concatenation of 2k and 18
- 2 × 1000 × 18 = 36000, since numbers and alphabets grouped together looks like multiplication
- 2.18k = 2180, just like 4k7 ohm means 4.7 kiloohm in electronics
(Thanks to the comment of Mr. Akshay Padhye on this Quora thread for reminding the 2.18k issue. Although I knew about the electronic notation, I hadn't thought about applying it to 2k18.)