Get-eventlog

Get-Eventlog "System" |
Where-Object {$_.EntryType -eq "Warning"} |
Where-Object {($_.TimeWritten).Date -eq (Get-Date).today}| ConvertTo-HTML |out-file D:\dreport.html

get-eventlog system -after (get-date).AddHours(-48) -EntryType Error,Warning | ConvertTo-HTML |out-file D:\warningreport.html

get-eventlog security -After (get-date).AddHours(-24) | ConvertTo-HTML |out-file D:\eventsecurity.html