In order to copy a spell into a spellbook the PHB states:
A wizard can also add a spell to her book whenever she encounters one on a magic scroll or in another wizard’s spellbook. No matter what the spell’s source, the wizard must first decipher the magical writing (see Arcane Magical Writings, above). Next, she must spend a day studying the spell. At the end of the day, she must make a Spellcraft check (DC 15 + spell’s level)...
...If the check succeeds, the wizard understands the spell and can copy it into her spellbook (see Writing a New Spell into a Spellbook, below).
This segment states:
Writing a New Spell into a Spellbook Once a wizard understands a new spell, she can record it into her spellbook.
Time: The process takes 24 hours, regardless of the spell’s level.
So how long really does it take to copy a spell? A whole 48 hours of uninterrupted study? Without sleep? Or is the book simply suggesting the character spends their normal 8hr adventuring day studying and copying the scroll? The reason I ask is doing something like crafting a magic item clearly defines how long the spellcaster must work during the day:
The caster works for 8 hours each day. He cannot rush the process by working longer each day. But the days need not be consecutive, and the caster can use the rest of his time as he sees fit.
For things like scribing a scroll the book indicates it takes "one day" and does not specify hours. This is why the "24hr" phrasing gives me pause.