What's the difference between hereunto and thereunto?

Hereunto

Definition:

• (adv.) Unto this; up to this time; hereto.

Example Sentences:

• (1) In token whereof I have hereunto set my hand this tenth day of December, 1936, in the presence of the witnesses whose signatures are subscribed.

Thereunto

Definition:

• (adv.) Unto that or this; thereto; besides.

Example Sentences: