It's only 5pm but it's very dark outside.
まだ17時だけど外はすごく暗い
The days are shorter in the winter.
冬は早く日が落ちる。
It's 7pm but it's still bright outside.
もう19時なのにまだ外は明るい
日が落ちるのが遅いと言いたい場合は"the days are longer"と言います。
是非使ってみてください！
① It's only five o'clock but it's already dark outside
「① It's only five o'clock but it's already dark outside」は「まだ17時だけど外はすごく暗いって」になります。「まだ」は only でニュアンスを表します。
逆に、「It's already seven o'clock but it's still light outside!」は「もう19時なのにまだ外は明るい」になり、「もう」のニュアンスは「already」で表せます。
ジュリアン
まだ17時だけど外はすごく暗い、は以下のように英訳できます。
１）It's already dark outside at 5 pm!
＝５時なると外は暗い
Already ＝もうすでに
完了形によく使われるので、完了形でしか使えないと思われがちですが、現在形でも過去形でも使われ、とても便利な単語です。
２）It gets dark outside after 5 pm.
＝５時以降は外は暗い
Get = ～を得る、という意味ですが、「～になる」という意味でも使われます。
Get + 形容詞＝～になる
It gets hot =熱くなる
I hope it helps :)
It's only 5 in the afternoon, but it's already dark outside.
The sun has already set although it's only 5 p.m.
It's 5 o'clock in the afternoon, but the sun has already gone down.
We sometimes say, "in the afternoon" to describe p.m. So it's correct to say, "it's only 5 in the afternoon." Also, you can reverse the the order of the sentence and explain that the sun has already set although it's only 5pm. It expresses the same meaning. Also, saying that the sun has "gone down" is another way of saying that it has set, or that it is dark outside.
午後（p.m.）を表すときには、"in the afternoon"も使われることがあります。ですから、"it's only 5 in the afternoon"（まだ午後5時です）も正しい言い方です。
また、文章の順番をひっくり返し、"the sun has already set although it's only 5 in the afternnon"（まだ午後5時ですが、すでに日が沈んでいます）と説明することも可能です。意味は同じです。
また、"the sun has gone down"は、"the sun has set"（日が沈みました）の別の言い方です。
It's only 5pm but it seems like its 9pm, its so dark outside.
"It's only 5pm but it seems like its 9pm, its so dark outside."
In this expression you are exaggerrating a bit by saying this but at the same time you are trying to convey to your audience or people you are talking to how you feel. In this case you are surprised that its only 5pm but its so dark it seems as if it was later that what it really is 9pm.
例文
"It's only 5pm but it seems like its 9pm, its so dark outside."
（まだ夕方の5時だけど、夜の9時みたい。外は本当に暗い）
この表現ではやや誇張した言い方をしていますが、同時に自分の感じていることについて伝えています。この場合は、まだ5時だけど9時と思えるくらい暗いと驚いています。
The first expression is most commonly heard when people are commenting about daylight during the Fall/Winter season. In the first expression, the time is mentioned (5 PM) but also that it's amazing it's dark despite the time. "Out" is a more casual and shortened way to refer to "outside".
To be more specific, in the second phrase you can mention that it's dark outside because the sun sets or goes down early/sooner that usual. "Around 5PM" explains the time frame the sun goes down - if it's already dark by 5PM, then the sun has to set before or around that hour.
Either expression is acceptable, but the first one is definitely an exclamation whereas an explanation for why it's dark is made in the second phrase.
日本 
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アメリカ合衆国 
