Xiǎngdāngchū tā lái zhèlǐ de shíhou cái shíbā suì.
Think back - when he first came here, he was only eighteen.
Tips
usage
Sentence-initial set phrase that flags a flashback or nostalgic comparison with the present. Often paired with 如今 ('nowadays') in the next clause to highlight contrast: 想当初... 如今... ('back then... now...'). Carries a wistful or rueful tone.
