You use ces when it relates to an easily identifiable noun. In the example you quote, "these" relates to a more vague and general time rather than a concrete noun.

Ce sont de beaux temps. -- These are good times.
Ces vacances étaient merveilleuses. -- This vacation was marvelous.

Thank you. Would you be able to tell me if "these" is a demonstrative pronoun or demonstrative adjective? And also, would you be able to elaborate or point me towards a more technical explanation on why "these" can be translated as "ce" in certain cases?  

If followed by a noun, "ce/cette/ces" is a demonstartive adjective and agrees in number and gender with the noun. If followed by a verb (often times "est" or "sont") it is always "ce".