It is recommended that the bid receiving authority stamp the bids as received, to avoid a situation in which one bidders fumbles in trying to stamp their envelope and delays another bidder past the due time.
 
It used to be that functioning clocks and watches were always wrong. (At least a broken one was accurate twice a day.) They might be set according to the chimes of a large clock tower, but they immediately became out of sync. This was both understood and accepted. 
 
The clock used for receiving bids was expected to be wrong. All bidders would show up early enough to check the time and adjust their timepieces to suit. Everyone was then in sync and if you were late, you didn’t complain about the timepiece.
 
It was common to have an analog timepiece in a stamping device. The bid envelope was inserted and the time of receipt was stamped on the envelope. Alternatively, the time  and date were written on the envelope.
 
Nowadays, with everyone using cellphones electronically synchronized with a central time signal, it is expected that all timepieces will not only be accurate, but also be in synch. i.e. display the same time. It may be difficult to find a wall or desk clock in an office today. Who needs one when your cell phone, your desk phone, and your computer all display the time?
 
As accurate a modern time keeping is, your cell phone, desk phone and computer may each be synchronized to separate distinct time signals which may not be sync’d with each other. The timepiece used to receive bids may not be tied to a central time signal at all.
 
If you want to be synchronized with an external time signal, see the section at the end of this commentary.
 
Despite the changes, it still comes down to what is the time on the timepiece that will be used for the receipt of bids, and the availability of that timepiece to the bidders beforehand so they can determine how slow or fast it is compared to whatever timepiece they rely on.
 
In most cases, it won’t matter, but some bidders will always cut it close to the time limit to try to get that little bit better of a price. At some point in time, a few seconds will make a difference in whether a bid is on time or not. When that situation arises, you want to be sure that your bid documents were absolutely clear about location and time for receipt of bids and which timepiece governs the process.
 
The time and date stamp industry has kept pace with general developments. Stampers are available with analog or digital clocks, some are synchronized to atomic clock time signals, some offer a variety of time and date formats with multiple additional lines of text, at prices ranging from $200 to $600.
 
Many stampers are intended for use with card stock time cards. Make sure the one you use will handle an envelope with a thick bid document within it.
 
Many time pieces and most stampers are electric powered. Make sure the one you use will continue to operate during a power outage. If it is battery powered, put fresh batteries in before the day of the bid closing. As batteries discharge, some timepieces will run more and more slowly.

Syncing to an External Time Signal
 
The NRC has website location for their static web clock which is based on the time established by the cesium clock at the National Research Council.
 
You may also want to consider the NRC Java web clock.  Please note the correction factors that are required on the link for using the Java web clock.  Please see link; https://nrc.canada.ca/en/web-clock/
 
To synchronize your timepiece in situations or locations where direct access to NRC static web clock is not available, you may consider using one of the following alternative methods;

1.CBC daily time broadcasts, please see link; 
https://nrc.canada.ca/en
2.Telephone talking clock, please see link; 
https://nrc.canada.ca/en
3.Computer time and date, please see link; 
https://nrc.canada.ca/en
 
If you are synchronized to an external time signal, you can refer to the source of the external time signal in the bid documents so the bidders can do the same. An example of such wording follows:
 
“Bid closing time shall be established by the Frequency and Time Group of the Time Standard Institute for National Measurement of the National Research Council (NRC).  Bidders are encouraged to check the website: https://nrc.canada.ca/en/web-clock/for the correct time and refresh the screen each time the time is checked.  Bidders shall note that the time given on the website is based on Coordinated Universal Time (UTC) and the twenty-four (24) hour clock (military time).  Bidders shall make all adjustments for internet delays, and include Eastern Standard Time (minus five (5) hours from Coordinated Universal Time (UTC)), and for Eastern Daylight Saving Time (minus four hours from Coordinated Universal Time (UTC)) when “daylight saving time” is in use in the time zone at the place of bid receipt.”