“Era”, “age”, and “epoch”

What are the differences and relations between era, age, and epoch? For example, should I say one of these?

• We are now in the digital era.
• We are now in the digital age.
• We are now in the digital epoch.
• We are now in the Internet era.
• We are now in the Internet age.
• We are now in the Internet epoch.

Or should I use some other word?

I found this comparison, but it is all about geologic history.

In geological time, these terms have specific meanings, but otherwise, according to the Wiktionary, they have similar meanings.

From Wikipedia:

Eras are divided into periods, epochs and ages.
Era: several hundred million years
Epoch: tens of millions of years
Age: millions of years

For your question however, anything digital or Internet related is not going to qualify for any of these words using geological definitions, and the exact definitions of these words are much more relaxed.

"Era" is used colloquially to refer to any period of time with a name. (http://en.wikipedia.org/wiki/Era#Colloquial_.22eras.22).

It seems to be more common to call it the "Information Age", as evidenced by Wikipedia and Google search results:

Number of search results from Google:
digital age - 986 million
digital era - 309 million
digital epoch - 8 million
Internet age - 1010 million
Internet era - 126 million
Internet epoch - 7 million
information age - 1450 million

In non-geological contexts, the terms "age" and "era" are more commonly used than "epoch" in the kinds of usage you cite. I would say "age" and "era" are roughly synonymous and would imply time scales of from a few decades to a few centuries. However "epoch" does bring in more connotations of geological time, so it would imply much larger time scales of at least a few centuries.