Saturday 23rd July
Open University and General Interest (Education) Time - 02:00 - 02:30 (30 minutes long) When - Sunday 24th July on BBC 2 Building by Numbers. From facade to room dimensions, a look at some of the world's most beautiful buildings, showing how they all rely on mathematics for their proportions. (BBC Learning Zone, Subtitles)
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is do they mean Friday night / Saturday morning or Saturday night / Sunday morning?
"When - Sunday 24th July on BBC 2."
If it is the programme I think it is worth setting your recorder for.