adjective / adverb
daylong
DAY-long/ˈdeɪlɔŋ/
Lasting or continuing for a whole day.
The woman's daylong weaving continues from sunrise through midday to sunset.

Etymology
In this compound, long measures duration rather than physical length: something extends through a whole day. The same combination already meant “lasting all day” in Old English.
More examples
- We pack lunch for our daylong hike.
- Rain falls daylong, keeping us inside until evening.
- The daylong workshop includes several breaks.
Similar words
- all-day
- Used before a noun, rather than as an adverb.
- nonstop
- Emphasizes the absence of breaks, not a whole day's duration.