(1) I tried snails three years ago.

(2) I've tried snails.

These two sentences are used in one text to make the difference between reference time, speech time and event time clear. In the text is given this explanation: "It is clear that-the key difference is in the subjective focus (reference time). In (1) the focus is on the event, so reference time coincides with event time (R=E). In (2) it is on the present relevance (the speaker now knows what snails taste like), so reference time coincides with speech time (R=S)". I think that I understand event time and speech time but I have failed to understand what is meant by the term reference time. Could you explain to me in a dumbed way what reference time is.

  • I think it's possible to understand '... had left at ten ...' to mean that at ten the event of leaving had already occurred, i.e., it took place before ten. But I do agree that 'by ten' would be clear, i.e., the event of leaving took place before ten. [for the discussion below] – user38483 Jul 29 '16 at 10:44

This is probably best explained with a picture!
(I apologize for the quality of my illustration. :-)

The main point of the picture below (and of course, this answer) is to illustrate that we have more than one alternative to deliver our thoughts.

In the picture, the Event "I'm trying snails!" happened 3 years ago. That's our Event Time.

"I've tried snails" vs. "I tried snails three years ago" timeline

In alternative A, "I've tried snails", the speaker speaks the utterance Now. He looks back (or thinks back) into the past, and recalls that at some point before now (indicating by the arrow), he was trying snails! The speaking time, also known as Speech Time, is Now. His "I've tried snails" means that:

a) The Event Time is before Now. (ET < ST)
b) He uses Now as his reference point (Reference Time) to look at the event. (RT = ST)

In alternative B, "I tried snails three years ago", the speaker recalls what happened three years ago by linking his mind to that time (the recalling/linking is indicated by the dashed arrow). Thus, his Reference Time is "3 years ago". The speaking time (Speech Time) is Now. His "I tried snails three years ago" means that:

a) His Reference Time is "3 years ago". (RT < ST)
b) The event that he tried the snails (Event Time) coincides with his Reference Time. (ET = RT)

That's pretty much all about ST, ET, and RT!


This is the ‘model’ for speaking about time and tense put forward by Hans Reichenbach in Elements of Symbolic Logic, 1947.

It involves three moments in time: speech time, reference time and event time. These are what your text labels ‘S’, ‘R’ and ‘E’; I am going to call them ‘ST’, ‘RT’ and ‘ET’ for consistency with other answers I have written on ELL.

Think of your verb as a camera taking pictures of events on a timeline running from the past through the present into the future.

  • The position where your camera stands is the point in time where you speak or write your sentence: ST.
    (Note that in a conversation ST is ordinarily ‘now’, but if you are reading an old text that’s not the same as the ‘now’ when you are reading it. It’s the writer’s ‘now’.)
  • The direction in which you are pointing your camera is the time you are talking about: RT.
  • The position of the event you are photographing is the time at which the event occurs: ET.

In the English tense system, the ‘simple’ and ‘progressive’ constructions are said to be deictic (‘pointing’) tenses. They speak of events which occur at reference time, the time you are pointing your camera at. Your first sentence is an example.

I tried snails three years ago. . . . You are pointing your camera into the past (RT < ST) and speaking of an event, trying snails, which occurred at that time (ET = RT).

‘Perfect’ constructions, however, are relative tenses. They speak of events which occur before the time you are pointing your camera at.

I have tried snails. . . . Your reference time here, the time you are talking about, is the present: (RT = ST). But the event you name, trying snails, lies in the past: (ET < RT).

There is more about this at our tag-wiki on tense.

The advantage of this simple model is that it allows us to speak about time references in complicated utterances without confusing ourselves with terms like ‘past’, ‘present’ and ‘future’ which we use to label both times and verbforms.

You should be aware that there are other models which are derived from Reichenbach’s and use similar terms, but in different ways. CGEL, for instance, uses Tr, “time referred to”, as approximately the same thing as ET, but its To, “time of orientation”, and Td, “deictic time”, are not distinguished the same way as RT and ST; and it introduces an additional term, Tsit, “time of situation”, to incorporate discussion of grammatical aspect.


Perhaps looking at an extended example will help understand Reference Time (RT):

(E1) I tried snails on May Day three years ago. (E2) I was then studying to be a doctor and (E3) I had met Sally already, whom (E4) I would go on to marry.

The time of each event, E1 to E5, is indicated relative to “May Day three years ago,” that is May Day three years before Speech Time (ST). So “May Day three years ago” is the Reference Time (RT), the time relative to which all event times are given. The time of Event 1 (ET1) coincides with RT, ET2 straddles RT (starts at some unspecified time before RT and goes on to finish at some unspecified time after RT), ET3 is before RT, and E4 is after RT. (From what I’ve read the serious students of these things don’t think it important to distinguish between “straddling” and “coinciding” and would write ET3 < ET1 = ET2 = RT < ET4 < ST, but the more variation in the example the better.)

In the example above RT is very clearly indicated, May Day three years before ST. But it need not be so. Consider this other example:

(E1a) I have tried snails. (E1b) I remember it well. (E2) I was then studying to be a doctor and (E3) I had met Sally already, whom (E4) I would go on to marry.

Now we have two reference times: RT for events E1a and E1b, and RT’ for E2, E3, and E4. RT’ = ET1a, because the times of events ET2 to ET4 are indicated relative to “then”, the time of event E1a (when you actually tried snails). Namely, as before, ET2 straddles RT’, ET3 is before RT’, and ET4 is after RT’. For E1a and E1b the reference time RT coincides with the speech time, and ET1a is before RT and ET1b coincides with RT.

In your two examples, in (1) reference time is some day three years before speech time, and in (2) it coincides with speech time.


I've searched for "reference time coincides with event time" and one of the links returned by the search engine was this one.

From the examples in which the Reference time did not coincide with the Speech time or the Event time, we can see that the Past Perfect and Future Perfect tenses are instances that show what the Reference time is. Consider:

Our train had left at ten in the morning. (spoken at one in the afternoon)

The speech time (S) is 1 pm. The event time (E) is in the past, earlier than 10, since at 10 in the morning the train wasn't there already. The reference time (R) is ten in the morning.

Our train will have left at ten in the morning. (spoken at six in the evening on the preceding day)

The speech time (S) is 6 pm. The event time (E) is in the future, but earlier than 10, since at 10 in the morning the train will not be there. The reference time (R) is ten in the morning.

For other examples and to draw your own conclusion, see the link.

  • 1
    I think not. Both your examples would ordinarily be understood to be speaking of an ET at 10 am, with an RT of some time after 10 am, unspecified but recoverable from context. An RT of 10 am would be marked with by rather than at, and would ordinarily be placed before the named event: By ten in the morning our train had left. – StoneyB on hiatus Oct 3 '15 at 13:57

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