Period
Epoch, Era, Time Period
You have a period of time and it's called a period or era! Simple!
じだい
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.
今の時代は、インターネットで何でもかうことができます。
In this era, you can buy anything on the Internet.
明里は、わたしの大学時代の友人です。
Akari is my friend from college.
紫式部は、平安時代中期の女性作家かつ歌人です。
Murasaki Shikibu was a female writer and poet from the mid–Heian period.