Earliest time to apply citizenship

Kindly suggest me that when should be the earliest time that I can apply for citizenship.

Yes, three years of being a "resident in Canada" is absolutely required before you apply.

Ditto XPEH but the "run into trouble" part deserves emphasis and clarification:

If you do not meet the residency requirement as of the day you submit the application, your application will be returned. Most indications are that if you do this, when you again apply you will have very high odds of being subjected to RQ (residency questionnaire) and your application will be delayed, and by that, that means delayed by months or even years. That's what running "into trouble" mostly means.

Technically meeting the residency requirement, and especially so for someone relying on the application of factors that will allow for the grant of citizenship despite some absences from Canada during the relevant time frame, is also a formula asking for RQ and some delay, perhaps a long delay.


Residency Requirement

From CIC web page:

Time lived in Canada To become Canadian citizens, adults must have lived in Canada for at least three years (1,095 days) in the past four years before applying. Children under the age of 18 do not need to meet this requirement. You may be able to count time you spent in Canada before you became a permanent resident if that time falls within the four-year period.

Again, you must meet the Residency Requirement as of the day you submit the application. That is based entirely on the four years (1460 days not counting any February 29) immediately preceding the date you sign and submit the application. Time in Canada after that date does not count. Absences from Canada after that date may be examined and considered but not in terms of counting actual, physical days present in Canada during the relevant time frame, which, again, consists of the 1460 days immediately preceding the date you sign the application.

The only sure way to meet the residency requirement is, after establishing residency in Canada, is to be actually, physically present in Canada for more than 1095 days. This is worth repeating: being actually, physically present in Canada for more than 1095 days out of the 1460 days that count.

Practically speaking, do NOT apply until you have indeed lived in Canada for more than three years PLUS have been physically present in Canada for more than 1095 days (out of the immediately preceding four years).

You must accurately disclose the dates of all travel outside Canada in the application. If you have not been keeping a detailed log for your own records, begin compiling this information as best you can and from here on keep meticulous records. A complete and accurate travel disclosure is one of the more important elements in making the application.

If you were present in Canada before you became a permanent resident (for example, with a work permit), you may be able to count those days towards meeting the residence requirement and thus be eligible to apply as early as 2 years after you became a permanent resident (this would depend on your travel as stated above).

The only sure way to know is to fill the residency questionary.