diff --git a/src/time-and-attendance/time-tracker/shifts/services/shifts-update-delete.service.ts b/src/time-and-attendance/time-tracker/shifts/services/shifts-update-delete.service.ts
index 2a36dfa..bb71e23 100644
--- a/src/time-and-attendance/time-tracker/shifts/services/shifts-update-delete.service.ts
+++ b/src/time-and-attendance/time-tracker/shifts/services/shifts-update-delete.service.ts
@@ -146,30 +146,36 @@ export class ShiftsUpdateDeleteService {
     private normalizeShiftDto = async (dto: ShiftDto): Promise<Result<Normalized, string>> => {
         const bank_code_id = await this.typeResolver.findBankCodeIDByType(dto.type);
         if (!bank_code_id.success) return { success: false, error: 'Bank_code not found' }
-
-        const date = toDateFromString(dto.date);
-        const start_time = toHHmmFromString(dto.start_time);
-        const end_time = toHHmmFromString(dto.end_time);
-
-        return { success: true, data: { date, start_time, end_time, bank_code_id: bank_code_id.data } };
+        return {
+            success: true,
+            data: {
+                date: toDateFromString(dto.date),
+                start_time: toHHmmFromString(dto.start_time),
+                end_time: toHHmmFromString(dto.end_time),
+                bank_code_id: bank_code_id.data
+            }
+        };
     }
 
     private overlapChecker = async (shifts: ShiftDto[]): Promise<Result<void, string>> => {
-        for (const shift_a of shifts) {
-            for(const shift_b of shifts){
-                if((shift_a.date === shift_b.date) && (shift_a.id !== shift_b.id)){
-                    const has_overlap = overlaps(
-                        { start: toHHmmFromString(shift_a.start_time), end: toHHmmFromString(shift_a.end_time) },
-                        { start: toDateFromString(shift_b.start_time), end: toDateFromString(shift_b.end_time) },
-                    );
-                    if (has_overlap) {
-                        return {
-                            success: false,
-                            error: `SHIFT_OVERLAP`
-                                + `new shift:  ${shift_a.start_time}–${shift_a.end_time} `
-                                + `existing shift: ${shift_b.start_time}–${shift_b.end_time} `
-                                + `date:  ${shift_a.date})`,
-                        }
+        for (let i = 0; i < shifts.length; i++) {
+            for (let j = i + 1; j < shifts.length; j++) {
+                const shift_a = shifts[i];
+                const shift_b = shifts[j];
+                
+                if (shift_a.date !== shift_b.date) continue;
+                if (shift_a.id === shift_b.id) continue;
+                const has_overlap = overlaps(
+                    { start: toHHmmFromString(shift_a.start_time), end: toHHmmFromString(shift_a.end_time) },
+                    { start: toHHmmFromString(shift_b.start_time), end: toHHmmFromString(shift_b.end_time) },
+                );
+                if (has_overlap) {
+                    return {
+                        success: false,
+                        error: `SHIFT_OVERLAP`
+                            + `new shift:  ${shift_a.start_time}–${shift_a.end_time} `
+                            + `existing shift: ${shift_b.start_time}–${shift_b.end_time} `
+                            + `date:  ${shift_a.date})`,
                     }
                 }
             }