What is the proper usage of the word(s) "as of" and "at" when completing financial reports? I have seen it used both ways. I.e., row one of a table might say "Balance at October 14, 2003" or "Balance as of October 14, 2003". In column headings we use the words "for the period ended".
' at ' refers to a specific time.

' as of ' means the specific time for something to start from.

another equivalent is ' as from ' = ' as of 'Emotion: smile
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Sadly, 'as of' is quite often found in American writing. It is a silly expression, stiff and pompous. The 'of' is redundant.

Use 'at.' (The balance at October 14, 2003 was $25.)

Advice to all learners of English: Never use it in a sentence. Use 'at,' 'on', 'since,' or 'from'

The Balance on October 14 was $25.

He has stopped studying since September 1.

You should discontinue work from November 1.
Does as of. Dec 31st 2017 mean before it or after it?

eg The total number of students as of Dec 31st 2017 means the total as it was at that point in time.

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