It looks like we started capitalizing "New Year" around 1880, then around 1900 we started capitalizing the "Happy" as well. https://books.google.com/ngrams/gra

It looks like we started capitalizing "New Year" around 1880, then around 1900 we started capitalizing the "Happy" as well. https://books.google.com/ngrams/graph?content=happy+new+year%2CHappy+New+Year%2C+happy+New+Year&year_start=1800&year_end=2000&corpus=15&smoothing=3 https://books.google.com/ngrams/graph?content=happy+new+year... We always capitalized "Christmas," but "Merry" took the capital around the same time as "Happy," around 1900. https://books.google.com/ngrams/graph?content=merry+christmas%2C+merry+Christmas%2C+Merry+Christmas&year_start=1800&year_end=2000&corpus=15&smoothing=3 https://books.google.com/ngrams/graph?content=merry+christma...