Here’s how I break down the various eras of magic, these are all approximations. I believe there are 5 distinct eras to the game. This is how I view each era, and some reasons why I think these eras are unique. I didn’t get to play most of these eras, but from listening to other people and reading, these are the points of the game that seem to stick out the most.

Antiquity
Limited Edition Alpha (1993) through Homelands (Oct 1995)
The preblock and pre-protour era.
Deck design and theory were non-existent. Limited play was impossible and sets weren’t designed for limited. There was no real internet, no magazines, and people didn’t even know what cards were what rarity!

The Classic Era
Alliances-> Urza block (1996-1999)

Introduction of the block system
Introduction of the Pro-Tour
Pre-MTGO, Pre-Net decks
Pre-6th edition rules change.
Mark Rosewater begins designing cards.
Beginning of the Magic Invitational
Rarity symbols are printed on the card
Magic cards consist of varying power-levels, with most being unplayable and a few standout insane cards.
Korean Magic cards are briefly printed in this era
Magic Theory consists of something called “Investment”

The Middle-Ages
Classic 6th Edition (1999)->8th edition (June 2003)

Theory of the game advances with “Who’s the Beatdown”
6th Edition rules change introduces the stack and cleans up the game
Foiling begins
Pre-MTGO grinding (MTGO launches in late 2002 and is completely under WotC with the release of 8th)
Last of the old card frames
Team Rochester
Dual lands rotate out of Extended
Introduction of Fetch Lands and Storm
R&D begins to take a much more active attempt to ‘balance’ Constructed after Urza block
In the storyline, the two major arcs of the game (Urza’s full Saga, and Kahmal) come to a conclusion, marking the “end” of long term multi-set stories.

Theory reaches the level of Philosophy of Fire

The Scientific Revolution
8th -> Time Spiral block (June 2003-Oct 2006)

Magic Online becomes a global game played by tens of thousands.
Various rules updates such as the 8th edition update and legend rules help clean up the game
Magic reaches its height in popularity with Mirrodin, only to see a crash due to Affinity and Kamigawa blocks. It’s not until the Modern Era that magic recovers.
The sets take place almost entirely outside Dominara, with a whole new cast and stories tangently connected to the previous fantasy.
With a few banned exceptions, the power of the cards begins to approach parity.
Magic is released in Russian. Magic has been printed in English, Italian, German, French, Spanish, Portuguese, Japanese, Traditional Chinese, Simplified Chinese, Russian, and Korean.
The magic invitational is held online, before ending in 2007 in one last face to face tournament.
Power level Errata is removed from most cards, but a few critical exceptions remain
This era marks the end of white-bordered cards
Last of the Un sets
Last of the Core sets released every 2 years
Last block without a planeswalker
The only THG pro tour takes place in this era

The modern color pie is set in stone in Future Sight, and the set cleans up magic by adding many evergreen keywords to the game, including Lifelink, Reach, Deathtouch, and Shroud.

The introduction of Damnation and then Tarmogoyf are portents of new directions in the power level of the game.

The theory in this era is driven by the discovery of Deck Advantage.

The Modern Era
2007-Today

Planeswalkers change everything
The Price of standard decks break $500, then $1000 for lots of reasons, including the introduction of constructed flagship mythics.
Magic content includes books and songs and youtube and podcasting, and eventually streaming of live tournament games.
Creatures begin to take precedence, both for their use against planeswalkers, and because of the push by R&D. Some of the most insane creatures have been printed in the past 4 years, and most of them aren’t even good enough to play outside of limited.
Magic online and the major tournaments push the talent of the game There is a major cash tournament happening every week in the United States, and daily tournaments are available online for almost every format of the game.
Commander becomes a major casual format
Introduction of Event Decks, and overall changes to FNM and the DCI try to push more players to their local gaming store.
Private Pro Tours
Printing of From the Vault, Duel decks, and Summer products like Planechase, ArchEnemy, and Commander
Duels of the Planeswalkers becomes a best selling game on X-box marketplace, encouraging multiple expansions and a sequel.
While there are lots and lots of super good cards in magic, Standard become dominated by a key dozen which the whole metagame will revolve around.
Extended is first shrunk, then abandoned as a format, due to balance issues and lack of interest
Introduction of the “Modern” format
The heavy uptake of Twitter by the community
Legacy blossoms with the SCG Open series, driving up demand for older cards. Since the start of the era there’s been a 400% price increase, or higher in some of the staples.
The greatest Standard deck of all time is discovered, resulting in the banning of the most expensive (Standard) card of all time.
WotC starts a major push with M10, the first yearly core-set, of making the game simpler in terms of mechanical difficulty. They have imposed many restrictions on themselves in terms of trying to reduce complexity creep that are obvious if you know what to look for. They also have begone removing unnecessary complexity baggage, such as removing mana burn.
Amateur traders are able to reach celebrity and profit on the back of just collecting and trading valuable cards, reminding us all that this is a Collectible Trading card-game.

Theory explodes beginning with “Breakdown of theory”; “All of magic is Interaction”; “there is no such thing as power”; The Unified Field Theory; and Card Advantage is Irrelevant. The best decks of the era all involve using the best mana, the best redundancy, multiple angles of attack, multiple defenses, and inevitability.

The technology we have to build decks is ridiculous In terms of knowledge of the game, 24/7 available testing environments, online resources, personal card databases, instant access to accurate rulings on cards and faqs, and access to judges. This is just unprecedented.

How many years did it take people to break the first magic sets? How long would it take a modern-only deck designer like Smi77y to solve the same formats?
This is reflected in the decklists we see today. Players have gotten better at cracking the code of the sets. It used to take months to solve a format, only to have a brewer’s work undone by a new set release. Now we’re cracking sets in weeks.

The future Era
(M12?)

I’m not really sure if we’re going to mark the end of the Modern Era with the banning of Jace and Stoneforge or not, but it wouldn’t surprise me if this marks a turning point in the future of the game. I seriously doubt they’ll make a mistakes like Jace anytime soon, and maybe this will mark the end of the Planeswalker era, as players integrate how to combat them into their normal strategy of the game, as well as an overall shrinking of their power level.

We’re likely to see a Magic Online 4.0, perhaps with something like Cube Support
R&D has started casting their eyes on other formats of the game in order to improve and keep those healthy. Are cards like Mental Misstep just the beginning?
Legacy is just continuing to grow in popularity. Is type 1 the new type 2? Will The Modern format be a bust?
Could we see a Pre-Release Grand Prix replacing local store pre-releases?
Will Magic ever become mainstream?
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I really don’t know if my breakdown points are the most important, or if my eras is the correct way to think about it. This is just how I think about the history of magic. I’m sure as a magic writer you might have a different perspective. You might mark it by the dominate literature of the era: Duelist, TheDojo, Starcitygames, podcasts, and finally video. You might measure it in the professional personalities of the game, look at who was dominate and look at who was falling out of the game. Whichever way you choose to break it down, we’re, in your own words, “playing a different game then we were 5 years ago.” That’s what people mean when they talk about the modern era.

Good job on keeping the wind out of the mic, guys! +1