Scheduled tasks page inaccessible: DateTime::__construct(): Failed to parse time string

Applicable to:

Scheduled tasks page inaccessible with the following error:

CONFIG_TEXT: Internal error:
DateTime::__construct(): Failed to parse time string (2017-12-20 2.2:0:03) at position 16 (:): Unexpected character

Product issue:

#PPPM-7634 "Creating a scheduled task in Plesk and configuring the time it must be run in cron format no longer results in an error when a decimal number is used."
Fixed in:
- Plesk Obsidian (RC1 18.0.15 as #PPP-34022) 04 June 2019 (Linux)

Please consider updating your server:

If update is not possible for some reason you may try the following

temporary solution

Log into the server via SSH .
Create a backup of Plesk database:
# MYSQL_PWD=`cat /etc/psa/.psa.shadow` mysqldump psa -uadmin > psa_current.sql
Enter Plesk database:
# plesk db
Find the wrong value by selecting time-related values from ScheduledTasks table:
MYSQL_LIN: SELECT id,minute,hour,dayOfMonth,month,dayOfWeek FROM ScheduledTasks;

In this example, hour with with id =14 is a wrong one.
Update value with id=14:
MYSQL_LIN: UPDATE ScheduledTasks SET hour=2 WHERE id=14;