In this post, I listed valid day values of some NLS_DATE_LANGUAGE other than AMERICAN and ENGLISH for you as a reference in order to solve ORA-01846: not a valid day of the week in SQL statements with TO_DATE function.
As for valid values of week days, you may check: Valid Month Values for Different NLS_DATE_LANGUAGE.
Please not that, the first day of a week (1-7) may vary from territory to territory. For instance, in AMERICA territory, the first day of week is SUNDAY. For Islamic countries, the first day of week is Saturday.
For complete language to territory mapping in Oracle, you may check: NLS_LANGUAGE to NLS_TERRITORY Mapping Table.
If you like to know more valid day values on languages other than the above listed, please leave you message in the comment.
Europe Languages
FRENCH (NLS_TERRITORY=FRANCE)
| D | DAY | DY |
|---|
| 1 | Lundi | LUN. |
| 2 | Mardi | MAR. |
| 3 | Mercredi | MER. |
| 4 | Jeudi | JEU. |
| 5 | Vendredi | VEN. |
| 6 | Samedi | SAM. |
| 7 | Dimanche | DIM. |
GERMAN (NLS_TERRITORY=GERMANY)
| D | DAY | DY |
|---|
| 1 | Montag | MO |
| 2 | Dienstag | DI |
| 3 | Mittwoch | MI |
| 4 | Donnerstag | DO |
| 5 | Freitag | FR |
| 6 | Samstag | SA |
| 7 | Sonntag | SO |
ITALIAN (NLS_TERRITORY=ITALY)
| D | DAY | DY |
|---|
| 1 | Lunedì | LUN |
| 2 | Martedì | MAR |
| 3 | Mercoledì | MER |
| 4 | Giovedì | GIO |
| 5 | Venerdì | VEN |
| 6 | Sabato | SAB |
| 7 | Domenica | DOM |
SPANISH (NLS_TERRITORY=SPAIN)
| D | DAY | DY |
|---|
| 1 | Lunes | LUN |
| 2 | Martes | MAR |
| 3 | Miércoles | MIÉ |
| 4 | Jueves | JUE |
| 5 | Viernes | VIE |
| 6 | Sábado | SÁB |
| 7 | Domingo | DOM |
Asia Languages
JAPANESE (NLS_TERRITORY=JAPAN)
| D | DAY | DY |
|---|
| 1 | 日曜日 | 日 |
| 2 | 月曜日 | 月 |
| 3 | 火曜日 | 火 |
| 4 | 水曜日 | 水 |
| 5 | 木曜日 | 木 |
| 6 | 金曜日 | 金 |
| 7 | 土曜日 | 土 |
KOREAN (NLS_TERRITORY=KOREA)
| D | DAY | DY |
|---|
| 1 | 일요일 | 일 |
| 2 | 월요일 | 월 |
| 3 | 화요일 | 화 |
| 4 | 수요일 | 수 |
| 5 | 목요일 | 목 |
| 6 | 금요일 | 금 |
| 7 | 토요일 | 토 |
SIMPLIFIED CHINESE (NLS_TERRITORY=CHINA)
| D | DAY | DY |
|---|
| 1 | 星期日 | 星期日 |
| 2 | 星期一 | 星期一 |
| 3 | 星期二 | 星期二 |
| 4 | 星期三 | 星期三 |
| 5 | 星期四 | 星期四 |
| 6 | 星期五 | 星期五 |
| 7 | 星期六 | 星期六 |
TRADITIONAL CHINESE (NLS_TERRITORY=TAIWAN)
| D | DAY | DY |
|---|
| 1 | 星期日 | 星期日 |
| 2 | 星期一 | 星期一 |
| 3 | 星期二 | 星期二 |
| 4 | 星期三 | 星期三 |
| 5 | 星期四 | 星期四 |
| 6 | 星期五 | 星期五 |
| 7 | 星期六 | 星期六 |