┌──────────────────────────────────────┐
│Dim nowDate As Date: nowDate = Date                                         │
├──────────────────────────────────────┤
│月初日 = DateSerial(Year(nowDate), Month(nowDate), 1)                       │
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│Const 期首月 As Long = 4                                                    │
│期首日 = IIf(Month(nowDate) < 期首月, _                                     │
│             DateSerial(Year(nowDate) - 1, 期首月, 1),                      │
│             DateSerial(Year(nowDate), 期首月, 1))                          │
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│年初日 = DateSerial(Year(nowDate), 1, 1)                                    │
└──────────────────────────────────────┘