Spiritually, "beginning" happens when we first start new growth -- new levels of awareness and willingness to receive goods and truths from the Lord, and use them. In the Word, "beginning" doesn't just mean the beginning of something in time. In the inner sense, it means the initial phase of a spiritual state.

8400. 'On the fifteenth day of the second month' means this state considered in relation ... This is clear from the meaning of the number 'fifteen', from the meaning of 'day', and from the meaning of 'month'. 'Month' means the end of the previous state and the beginning of the next, thus a new state, 3814; 'day' means a state in general, 23, 487, 488, 493, 893, 2788, 3462, 3785, 4850, 7680, and 'the fifteenth' means that which is new. For 'fourteen days' or two weeks mean a whole period or state from the beginning to the end of it, 728, 2044, 3845; 'fifteen' therefore means something new, in this instance newness of life, meant by the manna which they received from heaven, 'manna' being the good of truth, which is the life of a spiritual person. Fifteen is similar in meaning to eight, because the eighth day is the first day of a following week. For the meaning of 'the eighth day' as any beginning whatever, thus something new that is distinct and separate from what has gone before, see 2044, 2866; and for the fact that all numbers in the Word have spiritual realities as their meaning, 482, 487, 575, 647, 648, 755, 813, 1963, 1988, 2075, 2252, 3252, 4264, 4495, 4670, 5265, 6175.