> How do they schedule the shows to account for the odd lengths?
Certainly up through the 90s the 'big ticket' and imported shows started on the hour or :30 and everything else slotted around that. Secondary programmes often started at :50 or :15 as a result.
https://www.transdiffusion.org/content/uploads/2016/10/19991...
If timings were really awkward they would pad five or ten minutes with a short filler about hot air ballooning or pottery making or somesuch