Rollup merge of #79884 - Digital-Chaos:replace-magic, r=m-ou-se
Rollup merge of #79884 - Digital-Chaos:replace-magic, r=m-ou-se

Replace magic numbers with existing constants

Replaced magic numbers in `library/core/src/time.rs` with predefined constants.

aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust