[sentence]。ちなみに、[sentence]。
Standalone conjunctive expression; placed at the beginning of a new sentence to add supplementary information related to the preceding statement.
ちなみに is a conjunctive expression meaning "by the way," "incidentally," or "for your reference." It is used to add supplementary or related information to what has just been said. Unlike ところで, which changes the topic entirely, ちなみに stays connected to the current topic and offers additional details that the speaker thinks may be useful or interesting.
ちなみに typically appears at the beginning of a new sentence or clause, introducing a piece of information that is related to the preceding statement but not essential to it.
A common point of confusion is the difference between ちなみに and ところで. ところで is used to change the subject entirely, while ちなみに adds supplementary information related to the current topic. Using ちなみに to introduce an unrelated topic sounds unnatural.
In the example above, ところで would not be appropriate because the added information is directly related to the topic of holidays.
ちなみに is appropriate in both formal and casual settings. It is used in business conversations, presentations, writing, and everyday speech.