Jira has a great and clear way of doing this when entering time estimates in the task estimate field, simply using 1 letter after the weeks (w), days (d), hours (h) and minutes (m).

By not allowing a user to enter decimals, visualizing and reading the data is much easier.

For example, if a user adds 1,50h would they mean 1 hour and 50 minutes or 1 hour and 30 minutes? Jira solves this cleverly by chopping it up in the various units directly.

Examples of what can be entered:

• 1w 4d 1h 30m


• 4d 1h 30m


• 1h 30m


• 1h


• 30m

You can specify a time unit after a time value 'X', such as Xw, Xd, Xh
or Xm, to represent weeks (w), days (d), hours (h) and minutes (m),
respectively.

From Jiras logging work and time tracking guides

This may differ with each organisation depending on how they set it but its a good, clear example of this.

Standard format for time (and time intervals less than 24 hours in duration) is set by ISO 8601.

Using extended format (hh:mm[:ss]) fits best (note :!), clearly conveying time nature of the value.

From my experience, even though it says:

Decimal fractions may be added to any of the three time elements. However, a fraction may only be added to the lowest order time element in the representation..

using a fraction may lead to ambiguous interpretation.

HH:mm gives you shortest (only 5 charachters in width) and cleanest widely recognizable format.

I don't have enough reputation to comment so this answer is intended to add additional context to Astrogator's (Though I do think that Owen Hughes has provided the best answer from a UI perspective).

Astrogator's answer is misleading in that it conflates "time" (the absolute value of the time of day in a given time zone) with "duration" (the amount of time that something may take to complete)

ISO 8601 defines the following standard format for a time duration:

PnYnMnDTnHnMnS

where:

• P denotes that this is a duration (period) of time


• n is the amount of that size interval that is included


• Y/M/D designate Years, Months and Days respectively (also W for Week)


• T separates the day and larger units from sub-day units (time)


• H/M/S designate Hours, Minutes and Seconds respectively


• Any unit with a zero value can be excluded (eg. P1D can be read as P0Y0M1DT0H0M0S) so long as at least one is included (eg. P is not valid for a zero-length period but P0S is)

In addition T must be included if the days and lager are zero in order to avoid ambiguity, this means that P1M describes 1 Month while PT1M describes 1 minute. Decimals are also accepted as P1.5H = P1H30M. It is valid as well to include a value greater than the size of the next unit, with the caution that P1DT1H and P25H may not be the same where the interval falls over a change in daylight-savings time - a duration of P1D takes you to the same time the following day but a duration of P24D would have an extra hour consumed or an hour skipped leaving you an hour different.

The end result of all this is that the ISO standard description of a 1 hour 30 minute duration would be P1H30M. However, whilst this format is great if you are familiar with the standard, it is obtuse to unfamiliar users and I believe as a result that the Jira approach recommended by Owen Hughes is the best approach for your use-case.

Additional answer – still use decimal notation in reports

In addition to displaying individual values like 4d 1h 30m as shown in the accepted answer, it needs to be said that in context of reports (or other lists with multiple values) it would be unacceptable:

Name           Hours

-----------------------------

Peter          4d 1h 30m

Joan           1d 30m

Thomas         2w

-----------------------------

Total          2w 5d 2h

Instead you want:

Name           Hours

-----------------------------

Peter           97.50

Joan            24.50

Thomas         336.00

-----------------------------

Total          458.00

Another note:

When going with accepted answer, in cases like
2w 1h

you might prefer
2w 0d 1h

what assures the user about number of days. You know, 2d 10s may look a bit weird. Let's pick hours and minutes as a base unit which is always present (at least one of them) and whatever goes to the left or to right, list all related units, even if zero.