1.
two days
A duration of two days.
二日 means both "two days" (duration) and "the 2nd" (date).
Usage
From the 11th onward, regular readings are used: 十一日, etc.
Days of the month (1-10)
These have irregular native Japanese readings:
Related Words
Related:
一日 (the first (day of the month))
Related:
三日 (three days)
Related:
〜間 (duration suffix 〜間)