Is there a reason why 午 and 年 look so similar? These words don't have meanings that are similar, but why do they look nearly identical? Is it just a coincidence?
Yes, this is a coincidence. Generally, if the modern shape is confusing, you need to go back further in time to look at characters' original shapes and purposes to make sense of what's going on. Also, the meaning noon for 「午」 is a phonetic loan; that is, the shape 「午」 represented a word that sounded similar to an unrelated existing word meaning noon, and the shape has nothing to do with the meaning noon.
「年」 originally depicted a person 「人」 carrying grain plants 「禾」 on their back, indicating the meaning harvest period &gt; year; check out Is the character 年 (or its etymology) related to the mythical beast in Chinese mythology? for the glyph origins of 「年」.

Glyph origins of 「午」




時期字體
字形
參考資料




商甲

餘1.1合集13475


商甲

後2.38.8合集34621


西周金

作冊䰧卣集成5432


西周金

縣妀簋集成4269


戰國・齊金

子禾子釜集成10374


篆

午部說文解字


西漢隸

秦射42武威漢簡


楷






「午」 originally depicted a large wooden pestle used to pound or de-husk grainy foods such as rice. The word that 「午」 originally represented is now written as 「杵」, formed by adding semantic 「木」 (wood), and 「午」 forms or formed parts of other characters such as 「舂」 (picture of two hands 「廾」 using a pestle 「午」 and mortar 「臼」 &gt; to pound, grind) and 「御」 (originally a picture of a kneeling person 「卩」 operating a pestle 「午」).
As mentioned earlier, 「午」 is a phonetically borrowed character for the word noon, as pestle does not have anything to do with noon.

There is a peculiar pattern across several older characters: blobs on a vertical line tend to expand outwards into horizontal lines, and this is a simplistic description of what happened to the shape of 「午」 as well. You may check out the following glyph evolution tables for comparison:

壬
十
土



References:

漢語多功能字庫
小學堂字形演變
國學大師

郭沫若《甲骨文合集》
中國社會科學院考古研究所《殷周金文集成》


宋・徐鉉等奉敕校定　漢・許慎《說文解字》