That Was Yesterday (extended version)
is most likely in the Key of B Major
Notes in B Major:
A#/Bb, B, C#/Db, D#/Eb, E, F#/Gb, G#/Ab
Chords in B Major:
B, C#m, Ebm, E, Gb, G#m, A#dim
This key can also be known as G#/Ab minor.
When it's used as a minor key, the minor key note is stressed more than the major key note. The same notes and same chords still apply.