Meaning of 境 in その日を境に


その日を境に

Why does this mean 'On that day', does 境 mean something other then
'boundary'/'area' in this sentence?




> 「その日を境{さかい}に」

「境」 in this phrase means a " **turning point** " where something changed.

What it is that changed must be explained (or at least implied) in the context
before this phrase appears.

> "Ever since that day..."




> 「その日を境{さかい}に」

「境」 in this phrase means a " **turning point** " where something changed.

What it is that changed must be explained (or at least implied) in the context
before this phrase appears.

> "Ever since that day..."

