fix: move offset adding complexity inside TimezoneDate

src/util/strftime.ts

@@ -143,7 +143,7 @@ const formatCodes = {
 export default function (inputDate: Date, formatStr: string) {
   let d = inputDate
   if (d instanceof TimezoneDate) {
-    d = new Date((+d) + d.inputTimezoneOffset * 60 * 1000)
+    d = d.getDisplayDate()
   }
 
   let output = ''
@@ -190,4 +190,8 @@ export class TimezoneDate extends Date {
       this.inputTimezoneOffset = this.getTimezoneOffset() + delta
     }
   }
+
+  getDisplayDate(): Date {
+    return new Date((+this) + this.inputTimezoneOffset * 60 * 1000)
+  }
 }