Two of the most common prepositions of time are 'for' and 'since'. They both express something that started in the past and continues in the present, but we use them differently. That can frequently lead to confusion in everyday speech. Here is a helpful guide to help you avoid this confusion.

For

'For' is used in sentences where the speaker is specifying the duration or amount of time. It expresses how long a particular thing or situation has been going on or happening. It can be used with all verb tenses.

For example:

• I have lived in Dublin for 5 years.

In the above sentence, you are stating that the amount of time you have been living in Dublin is 5 years.

Further examples:

• The meeting went on for 2 hours.
• I've been working at that bank for 15 years.

However, it is important to note that with 'for', the amount of time in question does not need to be exact. You could, for example, say something like:

• I haven't seen her for a very long time.

Since

'Since' is used when specifying the starting point of something. It expresses duration up to the present, indicating that something began in the past and is unfinished. It is usually used with the Present Perfect or Present Perfect Continuous tenses.

For example:

• I have lived in Dublin since 2008.

In the above sentence, you are stating that you started living in Dublin in 2008 and you still live there.

Further examples:

• Tom hasn't been to work since last week.
• The meeting has been going on since 9 am this morning.
• Claire has had that car since she was 20.

'Since' can also be used in the structure 'it is a (period of time) since'.

For example:

• It has been a year since I got married.

So, in summary, 'for' is used to specify the duration or amount of time a particular situation or thing has been going on, and 'since' specifies the starting point of something, indicating that it began in the past and is unfinished. The basic formula for using both correctly is as follows:

For + a duration of time

Since + a point in time, until now.

Further examples:

• I have been working at that company since 3 years. INCORRECT
• I have been working at that company for 3 years. CORRECT

• I have been employed for 2010. INCORRECT
• I have been employed since 2010. CORRECT