Invalid month day value string value cannot be – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch encounters an invalid date format, specifically an incorrect day of the month. This could be due to a wrong date format in the data being indexed or a mismatch between the date format in the data and the mapping. To resolve this, ensure that the date format in your data matches the format specified in your index mapping. Also, validate your data to ensure that all dates are correctly formatted before indexing. If the error persists, consider reindexing your data with the correct date format.

This guide will help you check for common problems that cause the log ” invalid month day value. string value [{}] cannot be ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “invalid month day value. string value [{}] cannot be” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 return 1;
 try {
 return Integer.parseInt(value);
 } catch (NumberFormatException nfe) {
 throw new ElasticsearchParseException("invalid month day value. string value [{}] cannot be"; value);
 if (token == XContentParser.Token.VALUE_NUMBER) {
 return parser.intValue();


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