Fully revert civicrm_event timestamp change

with smarty syntax fixed

civicrm/CRM/Upgrade/Incremental/sql/5.47.1.mysql.tpl

@@ -5,3 +5,10 @@ DELETE FROM civicrm_navigation WHERE url='civicrm/report/list?compid=5&reset=1';
 
 DELETE FROM civicrm_managed WHERE module = "civigrant" AND entity_type = "OptionValue"
 AND name LIKE "OptionGroup_grant_type_%";
+
+{* Revert a90c3874d6ea74017dd038cc64d952afe99a1981 *}
+ALTER TABLE `civicrm_event`
+  MODIFY COLUMN `start_date` datetime NULL DEFAULT NULL COMMENT 'Date and time that event starts.',
+  MODIFY COLUMN `end_date` datetime NULL DEFAULT NULL COMMENT 'Date and time that event ends. May be NULL if no defined end date/time',
+  MODIFY COLUMN `registration_start_date` datetime NULL DEFAULT NULL COMMENT 'Date and time that online registration starts.',
+  MODIFY COLUMN `registration_end_date` datetime NULL DEFAULT NULL COMMENT 'Date and time that online registration ends.';

civicrm/CRM/Upgrade/Incremental/sql/5.47.alpha1.mysql.tpl

@@ -17,15 +17,7 @@ ALTER TABLE `civicrm_navigation`
   MODIFY COLUMN `weight` int NOT NULL DEFAULT 0 COMMENT 'Ordering of the navigation items in various blocks.';
 
 {* https://lab.civicrm.org/dev/core/-/issues/2122 *}
-UPDATE `civicrm_event` SET `start_date` = NULL WHERE `start_date` < 19700102;
-UPDATE `civicrm_event` SET `end_date` = NULL WHERE `end_date` < 19700102;
-UPDATE `civicrm_event` SET `registration_start_date` = NULL WHERE `registration_start_date` < 19700102;
-UPDATE `civicrm_event` SET `registration_end_date` = NULL WHERE `registration_end_date` < 19700102;
-ALTER TABLE `civicrm_event`
-  MODIFY COLUMN `start_date` timestamp NULL DEFAULT NULL COMMENT 'Date and time that event starts.',
-  MODIFY COLUMN `end_date` timestamp NULL DEFAULT NULL COMMENT 'Date and time that event ends. May be NULL if no defined end date/time',
-  MODIFY COLUMN `registration_start_date` timestamp NULL DEFAULT NULL COMMENT 'Date and time that online registration starts.',
-  MODIFY COLUMN `registration_end_date` timestamp NULL DEFAULT NULL COMMENT 'Date and time that online registration ends.';
+{* removed civicrm_event schema changes *}
 
 {* Ensure CustomGroup.name is unique *}
 UPDATE civicrm_custom_group g1, civicrm_custom_group g2 SET g1.name = CONCAT(g1.name, '_1') WHERE g1.name = g2.name AND g1.id > g2.id;