昨日の敵は今日の味方

Excite翻訳: Yesterday's enemy is an ally today.
@nifty翻訳: World may be topsy-turvy in an hour
Babel Fish: As for enemy of yesterday present friend
Google翻訳: Yesterday's enemy is today's ally
Yahoo!翻訳: The yesterday's enemy is today's friend
OCN翻訳: Yesterday's enemy is today's supporter.
Windows Live Translator: Yesterday's enemy is today ally

Summary:
Direct translation can make sense, but @nifty has a special expression.

Reverse Translation)
Excite翻訳: 今日、昨日の敵は同盟国です。
@nifty翻訳: 世界は1時間で逆かもしれません。
Babel Fish: 昨日の現在の友人の敵に関しては
Google翻訳: 昨日の敵、今日の味方です
Yahoo!翻訳: 昨日の敵は、今日の友人です
OCN翻訳: 昨日の敵は今日のサポーターです。
Windows Live Translator: 昨日の敵は今日の味方

Summary:
Excite, Google, and Windows produce different expressions from the same one.
Windows' is exactly the same as the original.