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web-admin/src/utils/protocol-payment-installment.ts

@@ -1,5 +1,7 @@
 /** 分期缴费：期数对齐、应缴日/金额计算（与 ProtocolFormDialog 逻辑一致） */
 
+const DAYS_PER_MONTH = 30
+
 export function addMonthsYmd(dateStr: string, months: number): string {
   const compact = String(dateStr || '').replace(/-/g, '')
   if (compact.length !== 8) return ''
@@ -28,13 +30,34 @@ export function addDaysYmd(dateStr: string, days: number): string {
   return `${yy}${mm}${dd}`
 }
 
-/** 分期应缴费时间：第 1 期=开始时间，第 2 期起在按月递增基础上提前 10 天 */
+/** 整数部分按日历加月，小数部分按 30 天/月换算为天数 */
+export function addIntervalMonthsYmd(dateStr: string, totalMonths: number): string {
+  const compact = String(dateStr || '').replace(/-/g, '')
+  if (compact.length !== 8 || !Number.isFinite(totalMonths) || totalMonths === 0) {
+    return compact.length === 8 ? compact : ''
+  }
+  const wholeMonths = Math.trunc(totalMonths)
+  const fracMonths = totalMonths - wholeMonths
+  let result = compact
+  if (wholeMonths !== 0) {
+    result = addMonthsYmd(result, wholeMonths)
+  }
+  if (fracMonths !== 0) {
+    const days = Math.round(fracMonths * DAYS_PER_MONTH)
+    if (days !== 0) {
+      result = addDaysYmd(result, days)
+    }
+  }
+  return result
+}
+
+/** 分期应缴费时间：第 1 期=开始时间，第 2 期起在间隔递增基础上提前 10 天 */
 export function calcFqInstallmentDueDate(
   startDate: string,
   index: number,
   intervalMonths: number
 ): string {
-  const base = addMonthsYmd(startDate, index * intervalMonths)
+  const base = addIntervalMonthsYmd(startDate, index * intervalMonths)
   if (index >= 1) {
     return addDaysYmd(base, -10)
   }