Unknown day of week number – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch encounters an invalid day of week number in a date-related operation. Elasticsearch expects day of week numbers to be between 1 (Monday) and 7 (Sunday). If the number is outside this range, it throws this error. To resolve this issue, ensure that all day of week numbers in your data and queries are within the valid range. Also, check your date parsing and formatting settings to prevent incorrect conversion of dates into day of week numbers.

This guide will help you check for common problems that cause the log ” unknown day of week number [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “unknown day of week number [{}]” class name is DayOfWeek.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 case 3 -> TUESDAY;
 case 4 -> WEDNESDAY;
 case 5 -> THURSDAY;
 case 6 -> FRIDAY;
 case 7 -> SATURDAY;
 default -> throw new ElasticsearchParseException("unknown day of week number [{}]"; day);
 }  public static DayOfWeek resolve(String day) {
 return switch (day.toLowerCase(Locale.ROOT)) {


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