"I almost forgot her birthday!"

Translation: 我几乎忘记了她的生日！

[WillowsofXihu]

In this case, 差（一）点 would be a better translation than 几乎 for "almost".

[GeneralXia]

Chinese speaker here. 差點 adds more emotion as if you feel bad that you just missed something. 幾乎 is more neutral and just states the fact that you missed something, but you aren't necessarily making a big deal out of it.

[tokititok]

I agree

[bekbok360]

I agree

[Gabrielle145359]

Why is 了 in this sentence?

[GanXingba]

I thought it was to mark the past tense of forget, or "forgot" 忘记 vs 忘记了

[KX3.]

忘记和忘了在这里用法一样啊

[YoungSiger]

'忘记'用'忘'应该也可以

[JamesHsuan1]

I think "了" can be also placed before ”她”

[eugenetehyj]

I omitted 了

[FonnyTejo]

为什么有了啊？那个句子是不是说还没发现的事情，所以我觉得不用了的话也可以。

[yuxqii._]

I don't think that it's common for natives to use ''几乎'' in a sentence. Plus I am one, and i've never heard of any of my family say that.