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+++ b/README.md
@@ -158,6 +158,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Hebrew Calendar](https://www.hebcal.com/home/developer-apis) | Convert between Gregorian and Hebrew, fetch Shabbat and Holiday times, etc | No | No | Unknown |
 | [Holiday API](https://holidayapi.pl/) | Enterprise-grade holiday and observance API for developers by developers | `apiKey` | Yes | Yes |
 | [Holidays](https://holidayapi.com/) | Historical data regarding holidays | `apiKey` | Yes | Unknown |
+| [Non-working Days](https://isdayoff.ru) | Simple API for checking working, non-working or short days for Russia, Ukraine, Belarus and Kazakhstan | No | Yes | Yes |
 | [Nager.Date](https://date.nager.at) | Public holidays for more than 90 countries | No | Yes | No |
 | [Namedays Calendar](https://api.abalin.net/) | Provides namedays for multiple countries | No | Yes | Yes |
 | [Non-Working Days](https://github.com/gadael/icsdb) | Database of ICS files for non working days | No | Yes | Unknown |