How long did Gandalf fight the Balrog for?

[Zyth]

Just as the subject says, I've been trying to figure out how long Gandalf was fighting the Balrog? (including how long he chased it for) If anyone knows, please help me out :)

[Legolas]

There's really no way to know, as indicated by Gandalf's account:

'Long time I fell,' he said at last, slowly, as if thinking back with difficulty. 'Long I fell, and he fell with me. [...] 'We fought far under the living earth, where time is not counted. Ever he clutched me, and ever I hewed him, till at last he fled into dark tunnels.'

[Lalaith]

According to Encyclopaedia of Arda, ten days. They fell together from the bridge on Jan 15th, and Gandalf cast the Balrog from Zirakzigil on Jan 25th.
Now, don't ask me how they worked that out. I'm hopeless with dates. :rolleyes: