In order to determine the date at which the recipients of the interest are determined, it is necessary to determine whether the gift was vested or contingent
A contingent interest is one that is subject to the happening of an event that may never occur.
A vested interest, on the other hand, is one the enjoyment of which is merely postponed, though it may be subject to subsequent divestment: see James MacKenzie, Feeney’s Canadian Law of Wills, 4th ed, looseleaf (Markham, Ontario: Butterworths, 2000-) at para. 17.2.
In other words, if the gift is subject to a condition precedent, then it is contingent; if it is subject to a condition subsequent (which will cause the interest to be divested if the condition is met), then it is vested subject to divestment. In this case, if the gift was contingent, the recipients would be determined as of the date the contingencies were satisfied. If it was vested, the recipients would be determined as of the date of the testator’s death.
A condition precedent establishing a contingent interest does not necessarily have to be personal to the donee; it can be a condition that some other person do some act or some other donee survive to a certain time: see Feeney’s Canadian Law of Wills at para. 17.6.
Usually, where the gift is contingent, the words of the condition precedent will be introduced by the word “if”: McKeen Estate v. McKeen Estate (1993), 132 N.B.R. (2d) 181, 49 E.T.R. 54 (Q.B.).
Where there is a gift-over in the event of death coupled with a contingency, such as “in the event of A’s dying without issue”, the gift-over will take effect when A dies and the contingency is satisfied:
Fraser v. Fraser (1896), 26 S.C.R. 316; Re Hildreth (1923), 54 O.L.R. 139 (C.A.); see also Re Fairfoull (1973), 41 D.L.R. (3d) 152 (B.C.S.C.), aff’d on reconsideration  6 W.W.R. 471, 18 R.F.L. 165 (B.C.S.C.).
The presumption of early vesting is that, wherever the words used in a will permit a construction that results in early vesting, the gift will be vested rather than contingent: Hamilton v. Hart (1919), 27 B.C.R. 101, 47 D.L.R. 231 (C.A.); Re Taylor,  3 O.R. 349, 28 D.L.R. (3d) 257 (H.C.J.).
Consistent with this presumption, where there is doubt as to whether a condition is intended to be a condition precedent or a condition subsequent, the court should prima facie treat it as a condition subsequent: Sifton v. Sifton,  A.C. 656,  3 D.L.R. 577 (P.C.).
However, the presumption only applies where the court has some doubt as to the testator’s intention: Re Fraser (1986), 55 O.R. (2d) 268, 29 D.L.R. (4th) 88 (H.C.J.); Henderson v. Henderson Estate (1990), 73 O.R. (2d) 616, 38 E.T.R. 120 (Ont. H.C.).
The rule in Browne v. Moody states that a gift of the remainder will be treated as vested if (a) it is postponed in the will solely for the convenience of the testator’s estate or (b) it is postponed by the creation of some prior interest, such as a life estate: see Re Thompson,  1 W.W.R. 289, 41 D.L.R. (3d) 305 (B.C.S.C.) and Re Ross (1984), 6 D.L.R. (4th) 193 (B.C.S.C.).