It is common for bidders to formally or informally ask for extensions to the bid submission deadline, claiming a lack of time to prepare the bids.
When one or more bidders request an extension, others might be ready to submit; therefore, an extension may produce an unfair disadvantage to those bidders who are prepared to submit on time. However, if an extension is not given, there may not be enough competition. The procuring authority should assess the situation and find a balanced response, taking into account any other external factors that may have delayed the bidders (such as extended public holidays).
In addition, an extension to the submission period may, like any other material change, be perceived by the market as a sign of volatility and lack of commitment by the government.
The best practice in terms of dealing with time issues is, as stated before, the setting of a realistic deadline based on a properly prepared project.