Extra Stage theme title
From the wikipedia article ハレとケ:
「ハレとケ」とは、柳田國男によって見出された、時間論をともなう日本人の伝統的な世界観のひとつ。
民俗学や文化人類学において「ハレとケ」という場合、ハレ（晴れ）は儀礼や祭、年中行事などの「非日常」、ケ（褻）はふだんの生活である「日常」を表している。
Roughly:
"Hare and ke" is a traditional Japanese outlook noted by by Kunio Yanagita.
From a folkloristic and cultural anthropology standpoint, hare (from 晴れ, in the sense of "formal") refers to ceremony and festivity, such as "out of the ordinary" events like annual feasts; ke (from 褻, "ordinary") refers to the ordinariness of day-to-day life.
So no, "Today will be sunny, but yesterday was not" is not the most appropriate translation.