をもってas of; by means of
Two jobs, and the word before tells you which. After a date or an occasion it is "as of": something officially ends there. After a means, a document or a quality it is a formal "by" or "with".
as of, said aloud
This concludes today's ceremony.
by
The final proposal will be decided by a vote.
As of
Date or occasion + をもって
本日, 三月末, 今回, これ, 以上 and the like. Said aloud at a ceremony or over a loudspeaker, it is often をもちまして.
By, with
Means, document or quality + をもって
書面, 投票, 実績, 誠意 and the like.
As of: something ends here
This is the voice of official notices: a shop closing for good, a service ending, someone stepping down. What follows is usually an ending, and the date named is the last day.
This facility will close as of 30 September.
I will step down as chair at the end of this fiscal year.
Ticket sales are now closed.
Our company will change its name as of April 1.
Sometimes it is a change that takes effect that day.
これをもって and 以上をもちまして wind up a speech, a meeting or a ceremony: "with that, we are finished".
With that, I declare the meeting closed.
A friend says で
This shop is closing for good today.
The notice on the door.
I hear this shop is closing down today.
Telling a friend.
Plain Japanese gives the date with で or に: 今月で辞める, 三月末に閉店する.
By, with: a formal で
After a means or a basis, をもって does the work of で in contracts, rules and official letters. A pencil, a bus or a phone stays with で.
We will inform you of the result in writing at a later date.
Sending out the prizes will stand in for an announcement of the winners.
The small print of a prize draw: no list of winners, the prize just arrives.
She proved her ability through her record over many years.
Three to learn whole
身をもってfirst-hand
Once I started living alone, I learned first-hand how much work housework is.
誠意をもってin good faith
We will respond to our customers' comments in good faith.
Formal: a company's stock promise to its customers.
自信をもってwith confidence
I can recommend this book with confidence.
Everyday, not formal. This one is the verb 持つ, "to have", and is also written 自信を持って.
をもってすれば and をもってしても
Both follow something impressive: a skill, a technology, great resources. With it, the thing can be done: をもってすれば. Even with it, the thing is hard: をもってしても.
With current technology, this margin of error can be greatly reduced.
Even with an expert's skill, this restoration will take several weeks.
Close neighbours
にてN2
Another formal で, lighter than をもって. It also marks a place, which をもって never does.
The training session will be held in the auditorium on the second floor of the main building.
を限りにN1
Names the last time, after which something stops for good. Final in tone: a firm resolution, or an ending announced with some regret. をもって is the same cutoff in official wording.
As of today, I'm giving up my nightly drink.
Check yourself
1In which sentence is をもって "by", not "as of"?
Choose an answer to see why.
2You are telling a friend about your gym. Which do you say?
Choose an answer to see why.
3Which one fits?
彼の
Choose an answer to see why.
More detail
In rules, AをもってBとする sets a standard: A counts as B.
A score of sixty or above counts as a pass.
Laws and older writing spell it with its kanji: を以て.
More sentences
Our company will discontinue sales of this product as of June 30.
I will step down from the committee when my term expires.
The closing ceremony brings the whole tournament to an end.
With the latest analytical technology, it is possible to identify the cause.
Even with the entire company's staff, finishing by the deadline would be difficult.