How does Microsoft Excel store dates?

Excel stores all dates as sequential floating-point serial numbers starting with serial 1 on January 1, 1900. Every whole integer increment represents one full day, and decimals represent hours and minutes (e.g., 0.5 = 12 hours).

Why do Excel dates sometimes display as numbers like 45281 in CSVs or databases?

When raw spreadsheet data is exported without date cell formatting, applications output the raw underlying serial integer. Converting this number restores the actual calendar date.

Does this tool account for Excel's 1900 leap year bug?

Yes, this converter accurately accounts for Lotus 1-2-3 compatibility rules (the historical 1900 leap year bug) implemented in standard Windows/Mac Microsoft Excel.

Time

Excel Date Serial Converter

Convert Microsoft Excel serial date numbers to human-readable dates and dates back to Excel serial values instantly.

Quick Answer & Summary

An Excel date converter translates spreadsheet serial numbers (like 46162) into calendar dates (like May 20, 2026) and vice versa. Excel stores dates as integers counting days since January 1, 1900, with decimal fractions representing time.

Excel Serial Date Formula

ExcelSerial = ((Date_UTC - 1899-12-30_UTC) / 86400000 ms) | Date = 1899-12-30 + (ExcelSerial × 86400000 ms)

Uses standard 1900 date system anchor offset (December 30, 1899).

Excel Serial to Calendar Date

Excel Number (e.g. 46162)

Readable Date

May 20, 2026

Calendar Date to Excel Serial

Select Date

Excel Serial Number

46266

Excel 1900 Date System

Microsoft Excel stores dates internally as continuous floating-point serial numbers where January 1, 1900 is day 1. Fractional values represent fractions of a day (e.g. 0.5 = 12:00 PM).

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Documentation & Guide

How to Use Excel Date Serial Converter

Convert Excel Serial Number

Type any 5-digit Excel serial number (such as 46162) into the box to see its human-readable calendar date.

Convert Date to Excel Number

Pick any date from the picker to find its exact numerical Excel serial value for formulas.

Copy with One Click

Click the copy button to paste directly into your spreadsheets or CSV exports.

Pro Tips

Essential when importing unformatted raw CSVs or SQL databases containing integer dates

Practical Examples & Conversions

Input

Serial 1

Output

January 1, 1900

Frequently Asked Questions (PAA)

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Authoritative Standards & Citations

Calculations and algorithms on this page are implemented and verified in strict accordance with the following official technical specifications:

International Organization for Standardization

ISO 8601: Date and Time Formats

Internationally accepted standard for representing dates and times.

Internet Assigned Numbers Authority

IANA Time Zone Database (TZDB)

Authoritative historical and current daylight saving time (DST) database.