observation vs observance

observation and observance both are nouns.

Word	Noun	Adjective	Verb	Adverb
observation	Yes	No	No	No
observance	Yes	No	No	No

As nouns, observation and observance are synonyms defined as:

Other synonyms of observation include watching.

As nouns, observation and observance are synonyms defined as:

Other synonyms of observation include notice.

observation (noun)	observance (noun)
the act of observing; taking a patient look	the act of observing; taking a patient look
the act of making and recording a measurement	conformity with law or custom or practice etc.
the act of noticing or paying attention	the act of noticing or paying attention
facts learned by observing	a formal event performed on a special occasion
a remark expressing careful consideration