Time of orientation and deictic time

I am confused about the difference between T_o and T_d in *CGEL's analysis of tense on page 126. Does T_d shift to the moment of decoding as T_o does in the second example?

1- I am writing this letter while the boys are at school. [T_o is time of encoding]

2- You are now leaving West Berlin. [a written notice] [T_o is time of decoding]

It is mentioned that T_d is "normally the time of utterance," but an exception is never explicitly stated.

* ^{The Cambridge Grammar of the English Language, Huddleston & Pullum (2002)}

Solution 1:

i. I am writing this letter while the boys are at school. [T_o is time of encoding]

ii. You are now leaving West Berlin. [a written notice] [T_o is time of decoding]

^{CamGEL, p.126, example (4).}

Yes, so-called deictic time is time where the present is the same time as the 'time of the utterance', the past is previous to it, and the future is the time after it.

Both examples (1) and (2) are examples of deictic time. What CamGEL are illustrating is that the 'time of the utterance' is not a clear cut simple affair. It may be the time something was written or recorded, or the time it is read or listened to (think of an announcement in a lift: 'you are on the first floor'). In both instances, the time reference may be deictic.

The easiest way to understand 'deictic' is perhaps that T_o is not interpreted in relation to some other verb or clause in the sentence. Consider:

• You will know you are in the right place.

In the sentence above, the verb are is the present tense instantiation of the verb BE, and represents a present simple construction. However, the present simple here doesn't indicate the time of the utterance. It refers to the same time as indicated by will know. In other words, we interpret the time indicated by are through the string will know. We don't undertsand are to be referring to the time of speaking or hearing. It isn't deictic in CamGEL's use of the term.