Shared parenting is where parents each have half or close to half of a child's parenting time.

For tax and child support purposes, shared parenting is where each parent has at least 40% of parenting time.

According to Dr. Nicholas Bala, Professor at Queen's Law (https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4058375)

...the pre-existing trend towards increased use of shared parenting has continued. Shared parenting now appears to be the most common parenting arrangement in in Canada in cases where both parents have had a significant role in the lives of their children before separation.

Shared parenting often takes the form of one week with one parent, the next week with the other parent, then repeating. However, it can take many forms. For example, one parent might have parenting time from Monday after school to Thursday each week, with the other having Friday to Monday morning parenting time.

Shared parenting is not a default. The only test that the courts consider in relation to parenting time is what is in the Best Interests of the child.

Shared parenting might be problematic where:

1. There are significant logistical hurdles (e.g. parents' residences are located too far apart from a convenient school or bus schedules, although some distance can be okay);
2. Where employment schedules do not accommodate daily parenting, even with the assistance of others;
3. Where siblings would be split (either due to differing preferences or the existence of half-siblings);
4. There is substantial conflict or a lack of communication and cooperation between parents, especially prior to trial (unless the parent making this argument is the principal source of conflict or cause for inadequate communication/cooperation). After a trial, this can also be overcome through Parallel Parenting or sole Decision-making;
5. It would otherwise not be in the children’s best interests, such as where a parent is a source of significant harm, has not been involved in the children’s lives for a prolonged period of time, is unable to provide for the children’s needs, doesn’t follow professional recommendations, or has an unsuitable residence (although the same level of luxury is not a necessity).

For an excellent summary of circumstances where courts have and haven't ordered shared parenting, see CAS v NPC, 2020 ABQB 421 at paragraphs 9 to 11.