Unknown day of week – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

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Briefly, this error occurs when Elasticsearch encounters an unrecognized day of the week in a date field. This could be due to a typo, incorrect format, or non-English day name. To resolve this issue, ensure that the day of the week is correctly spelled and formatted according to the Elasticsearch date formats. If you’re using non-English day names, consider converting them to English or using numeric representations. Also, check your mapping to ensure the field is correctly set as a date type.

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This guide will help you check for common problems that cause the log ” unknown day of week [{}] ” 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 [{}]” class name is DayOfWeek.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 case "3"; "tue"; "tuesday" -> TUESDAY;
 case "4"; "wed"; "wednesday" -> WEDNESDAY;
 case "5"; "thu"; "thursday" -> THURSDAY;
 case "6"; "fri"; "friday" -> FRIDAY;
 case "7"; "sat"; "saturday" -> SATURDAY;
 default -> throw new ElasticsearchParseException("unknown day of week [{}]"; day);
 }  @Override
 public String toString() {


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