Each date represents an observation log where the comet was observed (and in most cases, photographed).
Comet Machholz
Long Period Comet
Comet C/2006 A1 Pojmanski
Non-Periodic Comet
Comet C/2007 F1 LONEOS
Hyperbolic Comet
Comet 17/P Holmes
Periodic Comet
Comet C/2007 N3 (Lulin)
Non-Periodic Comet
Comet C/2013 R1 Lovejoy
Long Period Comet
Comet C/2014 Q2 Lovejoy
Long Period Comet
Comet 46P/Wirtanen
Short Period Comet
Comet C/2020 F3 NEOWISE
Long Period Comet
Comet 67P/Churyumov–Gerasimenko
Jupiter Family Comet
Comet C/2021 A1 Leonard
Long Period Comet