By some conventions (see ISO 8601), the Thursdays of a year determine the week numbering: week 1 is defined as the week that contains the first Thursday of the year, and so on.
In the popular rhyme, "Thursday's Child has far to go".
In the United Kingdom, elections are normally held on Thursdays.
In The Hitchhiker's Guide to the Galaxy by Douglas Adams, the character Arthur Dent says "This must be Thursday. I could never get the hang of Thursdays". A few minutes later the planet Earth is destroyed.