telomeres
Hover over the telomere bar on the left edge to see when a line was updated. Over time the bars will shrink in size depending on how old the line is.
Fun Fact:
"A telomere is a region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Its name is derived from the Greek nouns telos (τέλος) "end" and merοs (μέρος, root: μερ-) "part"." See https://en.wikipedia.org/wiki/Telomere