How to schedule a task in vCenter to start a Virtual Machine:

• Logon to vCenter → Tasks & Events → Scheduled Tasks
• Click on the “New” button
• In the “Schedule Task” dialog select the “Change the VM power state”
• In the “Change a Virtual Machine's Power State” dialog:
  • Select the virtual machine
  • Select the required Power Operation (Power on)
    • Note that it's possible to select a specific host to power on the virtual machine on.
  • Give a task name and description and set the the frequency (once - later - 20:00 - today)
  • Fill in the email addresses to notify after task completion

These are the options available when scheduling a task:

• Change the VM power state
• Clone a virtual machine
• Deploy a virtual machine
• Migrate a virtual machine
• Create a virtual machine
• Create a snapshot of a virtual machine
• Add a host
• Change cluster power settings
• Change resource pool or VM resource settings
• Check compliance for a profile
• Scan for Updates
• Remediate

The vCenter Server and ESX/ESXi hosts adhere to certain rules when managing tasks in the system.
vCenter Server and ESX/ESXi hosts use the following rules to process tasks:

• The user performing the task in the vSphere Client must have the correct permissions on the relevant objects. After a scheduled task is created, it will be performed even if the user no longer has permission to perform the task.
• When the operations required by manual tasks and scheduled tasks conflict, the activity due first is started first.
• When a virtual machine or host is in an incorrect state to perform any activity, manual or scheduled, vCenter Server or the ESX/ESXi host does not perform the task. A message is recorded in the log.
• When an object is removed from the vCenter Server or the ESX/ESXi host, all associated tasks are also removed.
• The vSphere Client and vCenter Server system use UTC time to determine the start time of a scheduled task. This ensures vSphere Client users in different time zones see the task scheduled to run at their local time.
• Events are logged in the event log at start and completion of a task. Any errors that occur during a task are also recorded in the event log.

Note: Do not schedule multiple tasks to be performed at the same time on the same object. The results are unpredictable.