this would also allow to compare two items and see which one has more recent value. it would be highly useful when having two items that receive snmp traps - and one gets "ok", another gets "error" traps.
A somewhat related issue: ZBX-4500.
I also need this kind of trigger function to test if i have recieved some data during a period.
For example, i want to check if i have data once a day from monday to friday, and send an alert on monday if there wasn't any data on friday.
that should be possible with nodata() function already
richlv: with nodata function, i can only check if i have no data during last "period".
I want to check if i have no data between last friday 00:00 and last saturday 00:00.
I have a related feature request _' :
Is it possible to add a {ITEM.LASTCLOCK} macro to inform users in notifications.
For example : "Last data collected at {ITEM.LASTCLOCK}"
well, the suggested feature would give you timestamp of the last value, thus it would not help you anyway.
as for the macro/variable, please, create a new feature request for that (searching for existing ones first 
)
I found a related feature request ZBXNEXT-1118 so i voted for it 
Hello,
I'm calling you again about this feature request.
I need to know the last clock of an item value to check if last item clock was before another item clock.
Do you think it's possible to add this new trigger function ?
it is currently not on the roadmap. fastest way to make it implemented would probably be financed development (see http://www.zabbix.com/development_services.php for detail)
(1) the function should support optional string that would allow to match last value with a specific string (or regexp)
see ZBXNEXT-2555 for the usecase
similar trigger function "age()" requested in ZBXNEXT-3680
Another example where this could be useful is including a number of latest values with corresponding timestamps in a notification message.
For instance, to send the last five values:
{host:item.unixtime(#1)}: {host:item.last(#1)}
{host:item.unixtime(#2)}: {host:item.last(#2)}
{host:item.unixtime(#3)}: {host:item.last(#3)}
{host:item.unixtime(#4)}: {host:item.last(#4)}
{host:item.unixtime(#5)}: {host:item.last(#5)}
The intention is to produce something like this:
2018.11.28 14:25:00: 75 % 2018.11.28 14:20:00: 48 % 2018.11.28 14:15:00: 33 % 2018.11.28 14:10:00: 31 % 2018.11.28 14:05:00: 9 %
Note that the timestamp is meant to be human-readable.
This is may also resolve feature request ZBXNEXT-7017.
I request {ITEM.TIME[0-9]} and {ITEM.LASTTIME[0-9]} so the trigger description for nodata() based expressions.
The idea would be that the time of the item collection can be used in the description for the 'Problem' ({ITEM.TIME[0-9]}) and the 'Recovery' ({ITEM.LASTTIME[0-9]}).