If the jail sentence is 90 days or less, the judge has the discretion to allow you to serve is intermittently. This means that you can go to jail on weekends, and still be able to go to work and/or take care of the kids during the week until the sentence is served. For example, if you go into custody on Friday at 7pm, and are released on Monday at 7am, you will get the benefit of 4 days custody. At this rate, even a 90 day jail sentence can be completed relatively quickly, and with minimal intrusion into your ability to earn a living.
Actual Jail is a sentence of last resort. When no other sentence is appropriate, either because of the nature of the offence, or because of your particular circumstances, a jail sentence will be imposed. A Jail Sentence will be served in either a Provincial Jail if there is less than two years left to serve on the day of sentence, or in a Federal Penitentiary for any sentence of two years or more.
The current system allows for automatic parole after two thirds of the sentence is served. That means that if a 1 year jail sentence is imposed, you will almost automatically be released after completing 8 months. Both the provincial and federal systems have early parole options, although the federal early release system seems more robust.
If straight jail is imposed on the day of sentence, there will be no opportunity to say your goodbyes or walk the dog. Make sure you have all your affairs in order before proceeding to sentence because once a jail sentence is pronounced, there is no going home until the sentence is served.