Both Sid and Jack acted like jerks. Former for her birthday and Jack for picking her and ruining her day. Really both should had taken into consideration there the birthday and him growing up so poor.
As they bond, and really Jack acted like a jerk by ordering pizza for himself that he did not bother to ask Syd. But later he reveals he does not know his birthday and apologizes for the way he had behaved.
Syd in the end gets her birthday and offers to share her birthday with Jack. That also means Z may not know her own birthday possibly.
Light episode and glad Syd took Jack into consideration there.
As they bond, and really Jack acted like a jerk by ordering pizza for himself that he did not bother to ask Syd. But later he reveals he does not know his birthday and apologizes for the way he had behaved.
Syd in the end gets her birthday and offers to share her birthday with Jack. That also means Z may not know her own birthday possibly.
Light episode and glad Syd took Jack into consideration there.