Counting days: in Canada as a visitor? in Canada with visitor status?
While the range of responses by others cover the essentials, this is another line of inquiry which warrants the reminder that technicalities are one thing, practicalities are another.
Technically a day in Canada is, ispo facto, a day present in Canada, and thus presence in Canada pursuant to legal status CAN be counted (this was NOT necessarily true under the old 3/4 residency rules).
But one can nonetheless ask, and in more than a few scenarios should ask, WILL? those days be counted?
For this particular question, while the matter of proof looms large, another important consideration has to do with the potential for triggering non-routine processing.
The latter, non-routine processing, does not necessarily mean there will be a negative outcome, but most applicants will prefer to avoid non-routine processing, both to avoid the inconvenience (especially the particularly inconvenient and intrusive RQ) and the inherent delays (which, depending on various factors, can be rather lengthy).
The matter of proof, however, can result in a negative outcome. Remember, if IRCC questions the applicant's accounting of days present, the burden is on the applicant to prove all the days claimed to have been in Canada. IRCC does not have to conclude, let alone prove, that the applicant was not in Canada for days to NOT count. If IRCC merely determines that the applicant has failed to affirmatively prove some days in Canada, those days will NOT count. In that event, the case goes to a Citizenship Judge, whose role is not to determine how many days the applicant was present in Canada, but to determine how many days the applicant has proven he or she was present in Canada.
If and when it comes to proving presence, such as in the event of being RQ'd, it warrants remembering that the applicant may no longer benefit from the inference of being present in Canada between a reported date of entry and the next reported date of exit. Routine applicants generally benefit from this inference. That is, they in effect get the benefit of the doubt, a conclustion that they were present in Canada between a reported date of entry and the next reported date of exit. Applicants with a presence case do not get the benefit of this inference, at least not nearly to the same extent as routinely processed applicants.
Not all visitors are created equal.
Note, for example, a FN can be residing in Canada even though his or her immigration status is that of a visitor. The most obvious example is the FN married to a Canadian who is sponsoring the FN for family class PR, the FN allowed to reside in Canada with visitor status pursuant to dual intent. There are other examples, seasonal residents for instance, persons who maintain a non-primary residence (typically a secondary or recreational residence) in Canada (I did this for many years prior to formally immigrating to Canada).
That distinction could have been a significant factor under the old 3/4 residency rules since technically no days in Canada counted until the applicant had established in-fact residence in Canada. Thus, even someone with PR status who only came to Canada briefly, more or less visiting, was not entitled to have days in Canada count until after having established an in-fact residence in Canada. (I have oft discussed elsewhere the nuances and parameters for enforcing this.)
While that distinction technically should not matter for a physical presence requirement, it likely looms relative to whether there is immigration documentation of status and presence, apart from and in addition to evidentiary documentation of physical presence.
Which leads back to recognizing that not all visitors are created equal. There is a big difference, for example, between the visitor who has a formal TRP or other formal immigration documentation confirming status and entry into Canada with that status, versus the visitor who was waived through the PoE without a referral to Secondary, without formal documentation of status or entry.
A common example: a visa-exempt visitor who is, for whatever reason, issued a Visitor's Record upon entering Canada. This can be common in the situation where a FN married to a Canadian has come to Canada to stay with his or her sponsoring spouse pending an application for PR. (And, indeed, I was such a FN, issued a VR while I was living with my sponsoring spouse pending my application for PR.)
The practical import of this is that when such formal immigration documentation exists, IRCC's own records for the client verify the entry, and thus support an inference of presence.
Without such formal documentation, IRCC is more likely to request the applicant provide evidence to document the entry and stay in Canada. The problem with this is that this knocks the application off the routine track, renders it a non-routine application. While perhaps in some cases there is minimal difference in how IRCC personnel view non-routine applicants versus routine applicants, my sense is that not only does non-routine processing inherently mean inconvenience and delays, at the least it probably increases the risk of elevated scrutiny if not skepticism.
Thus, it would be prudent to carefully consider the particular circumstances in one's situation before deciding to proceed with an application dependent on counting time in Canada as a visitor.
For some it will make sense to proceed. For others it probably will not be worth the risk of non-routine processing even if there is little or no doubt about obtaining a successful outcome. In this regard, one of the more foolish practices evident in forum reports is rushing to apply before the best time to apply. Reaching the threshold of eligibility is merely one factor (albeit a necessary one) to consider when deciding when is the best time to apply. (I practiced what I preach in this regard: I literally waited to apply nearly two years after the date I became eligible for citizenship. That is undoubtedly at the more unusual end of the spectrum, but in my personal situation that was indeed the prudent course to take.)
The short answer: yes, one can count days in Canada as a visitor, but prospective applicants should be cautious about whether they will actually get counted.