Oxford Duden

I think 'the terrible twos' is a good translation of 'Trotzphase' and equally descriptive. It should probably be followed by a 'coll.'

Langenscheid (Muret-Sanders) has 'phase of defiance, phase of obstinacy'.

speaking from experience, I'd say it should be the terrible twos, threes and fours at least...

Did you know that in German the age following the Trotzphase is also known as the "magisches Alter", as they believe in magic then? Lovely, don't you think?

The sayings go: "terrible twos", "thoughtful threes" ,"frightful fours" and "friendly fives". So I don't know if just the "twos" fits for "Trotzphase", though I agree that it's more or less the same idea but it would make sense to include the frightful fours as tanja1's parental wisdom suggests.

When I was a child I added "sensible sixes" to this list, though I'm not sure if this is a classic idiom. (I must have been six at the time, I daresay.) (Reminds me of the poem Now We are Six by A.A. Milne,

"...But now that I'm six
I'm as clever as clever-
I think I'll stay six now
for ever and ever!")

A tongue-in-cheek insult directed at myself

'Trotzphase' may also refer to the 'age of defiance' which runs concurrently or around the same time as puberty. My German insulter assured me that this was the intended meaning ('the terrible twos' would have made a better insult, if not somewhat hyperbolic).

It is unpleasant to have anyone passionately disagree with you. When this opposition comes from your own little delight, the situation is decidedly disagreeable. Many people call this important phase of development the "Terrible Twos." I prefer to call it "The First Adolescence." This period begins long before age two and actually continues long afterwards, but in the majority of children, it is most intensely focused around the period from one-and-a-half to three years of age.
http://www.drgreene.com/21_556.html

You may notice that the 'Terrible Twos' start a little before your child's 2nd birthday.
Your toddler is becoming increasingly negative and seems to object to everything you ask. The slightest upset can send her into a tantrum.
http://www.raisingkids.co.uk/1_4/tod_dev10.asp

Trotz|pha|se, die (Psych.): Trotzalter.
Trotz|al|ter, das <o.Pl.>: Phase in der Entwicklung des Kindes, in der es den eigenen Willen erfährt u. durchzusetzen versucht: unser Sohn ist jetzt im T. (B.Vesper, Reise 316).

© 2000 Dudenverlag

Excellent suggestion.

"She's going through a phase."

The problem with "terrible twos" vis-à-vis "Trotzphase" is that it's so limited. Cute, but a tad misleading (as others have noted), and in any event not applicable to other ages, e.g. adolescence. "Going through a phase" seems to be the favored more general locution in these parts (California). It always refers to spiteful or obstreperous phases, never to cooperative or blissful ones.

Gut, dann eben so.