complete reversal of values or thinking over time; realizing and regretting past errors
A yojijukugo expressing the idea that what one believed in the past now seems wrong, and what one believes now is right, often with a sense of regret or awakening. Used in reflective or philosophical contexts.
Looking back on the mistakes of his youth, he was overcome by a feeling of complete reversal of values.
My outlook on life has changed; it's truly a state of mind where past wrongs now seem right.
A similar proverbial expression meaning 'yesterday's wrong is today's right,' but less compact and less common as a set phrase.
From 陶淵明’s 帰去来辞, particularly the line 覚今是而昨非, “realizing that now is right and yesterday was wrong.” It expresses recognition and regret of one’s former error.