Audacity can export label track to plain text files (.txt). The standard structure of an exported label track is as follows:

SS.MMMMMM →  SS.MMMMMM  →  label at SS seconds and MMMMMM milliseconds
2.150000  →  2.150000  →  point label at 2.15 seconds
3.400000  →  6.100000  →  region label from 3.4 to 6.1 seconds

This webapp is an utility to convert a label track in Audacity to other time formats (e.g. youtube chapter description)

mm:ss - [Chapter Content]  for video lengths between 10 and 59 minutes

hh:mm:ss - [Chapter Content] for videos longer than 1 hour