Complex sentence: Apprentices were no longer permitted to work during the night (between 9pm and 6am); the Act gave factories time to adjust to this change and stated that all night-time working by apprentices was to be discontinued by June 1804.
Split into simpler sentences: Apprentices were no longer permitted to work during the night (between 9pm and 6am). A grace period was provided to allow factories time to adjust, but all night-time working by apprentices was to be discontinued by June 1804.