always; all the time; at any time
Emphatic colloquial expression meaning 'no matter when' or 'whenever'; often used in casual speech to stress that something is always true or happens without exception.
彼はいつだって遅刻する。
He's always late, no matter when.
いつだって君の味方だよ。
I'm always on your side.
Derived from いつ (when) + だって (even, also), a colloquial contraction of だといって or であっても, meaning 'even if it is when' → 'whenever, always'.