Green’s Dictionary of Slang

(US) the very best, the most memorable on record.

1940		Rotarian June 15: JIM THORPE, all-time ‘great,’ leads the field in the hurdle.
1952		Life 10 Mar. 131: Old-time, all-time great Ty Cobb.
a.1964		‘Honky-Tonk Bud’ in D. Wepman et al. Life (1976) 58: Now J.P. Spence was the hipcat’s defence, / And known as an all-time great.
1972		D. Jenkins Semi-Tough 152: I’ve known the all-time girl and I’ve loved her and she’s loved me.
1985		J. Wambaugh Secrets of Harry Bright (1986) 78: That waitress is all time [...] She’s the kind tries to lick you with her eyes.
1990		J. Wambaugh Golden Orange (1991) 175: She was all-time, that redhead!
2001		S. King Dreamcatcher 68: I’ve heard some mighty belches, but that’s an all-time blue ribbon winner.