Period
Era
noun, suffix
You learned 代 means "substitute," but it can also mean "period." And a time period is also called a period or an era. Simple!
時代 refers to a longer span of time, whether it's an historical period, the present times, distinct eras in pop culture, or personal life stages.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
今の時代でも、日本にはファックスが有ります。
Even in this era, there are fax machines in Japan.
これは、平安時代のラブストーリーの本です。
This is a book of a love story from the Heian period.
今の時代、インターネットが全てを教えてくれます。
In the current time period, the Internet will tell you everything.