1. there are two ways of thinking about time and events in it; one involves the A series and the other the B series.
 

1. In the A series, events (or time) are located in time on the basis of their relation of being 'earlier than,' 'simultaneous with,' or 'later than' the present , the 'now.'  Since the future is what is later than the present, and the past what is earlier than the present, events are arranged in the order in which they become present, that is on the basis of their tenses.  A tense is a position in the time series defined by its location (and distance) with respect to the present, the 'now'.  For example, 'tomorrow' is a tense because it's a day one day later than the present day.  Notice that the 'now' moves.

NOTES
• We commonly use tenses.  For example, if I say “he will marry”, or “the war ended” I convey that idea that the first event is in the future and the second in the past.  It's important not to confuse grammatical tense with philosophical tense: "tomorrow I go to school" is philosophically tensed.
• The A series is dynamic because things/events go from being future to being present, and then past. In other words, suppose that 'tomorow I'll be 50' is true.  Then, it won't always be true; in fact, the day after tomorrow it will be false. Hence, the tenses of events and things change.  Similarly, the truth values (the property of being true or false) of tensed statements change.
2. In the B series, events are located in time on the basis of the relations of 'being earlier than', 'being simultaneous with', and 'being later than' with respect to each other.  In practice (although this is not necessary in principle), one selects an event and arranges other events on the basis of their temporal distance and relation to a fixed event such the birth of Christ, the foundation of SIUE, or whatever.  A date is a position in the time series defined by its location (and distance) with respect to a fixed point.  For example, '1945' is a date because it's a year 1945 years later than the (traditional) birth of Christ.

NOTES:
• We commonly use dates, as in “the war ends in 1945”, "on the 5th I go home".
• The B series is static because if A is earlier than B, or occurs in 1945, that is always so. In other words, suppose that 'on March 11 2001 I'm 50' is true.  Then, it will always be true, even on March 12th.  That is, the dates of events and things don't change.  Similarly, the truth values (the property of being true or false) of tenseless statements don't change.

• Given the date of 'now', they are inter definable, that is, one can freely move from the A series to the B series and vice versa.
• They arrange things/events in the same order, that is, they are structurally identical.

• Tenses change but dates don't.
• Without date of 'now', the A series not reducible to the B series and vice versa.  One could know all the B-series history of the world without knowing which stage history has reached, i.e. what's happening now.  In this case, one would know dates but not tenses. Conversely, one could know the locations of all events with respect to now, without knowing the date of now.  One, then, would know tenses but not dates.

Notice that knowing dates but not tenses is not uncommon: I may know that the appointment is at 5 without knowing what time it is now because my watch stopped.  Note that this situation has a spatial analogue: have you ever looked at a map without knowing where the 'here', i.e., where you are, is? 
• “It is hot now” doesn't mean “its hot on the 2nd of August” even if ‘now’ is the 2nd of August.

1. The world is tensed but not dated: there are tensed facts but no dated facts.
2. The world is dated but not tensed: there are dated facts but no tensed facts (Russell; Quine; Mellor; Oaklander, etc.)
3. The world is both dated and tensed: there are both dated and tensed facts (Swinburne; Smith, etc.).

NOTE: this seems plausible: "WWII ended in 1945" seems to be made true by a dated fact and by a tensed fact.

A. Method of translatability
The claim here is that tensed sentences are eliminable because they are translatable into dated ones.  So, everything we could possibly say with tense we could say without it.  Hence, tense is eliminable (this was the strategy of the old tenseless theory).
NOTE: this assumes that linguistic analysis has metaphysical implications.
There are three different analyses of tensed statements which allegedly shows that they are translatable into tenseless ones:
 

1. token-reflexive analysis:

 “X is present” means “X is simultaneous with the utterance of the token ‘X is present’”.; etc.
Example: "it snows now" means "snowing is simultaneous with the utterance of 'it snows now'"
 
2. psychological analysis:

  “X is present” means “X is perceived or simultaneous with something perceived”; etc. (Russell; early Broad)
Problem for (1) and (2):
X could be present even if “X is present” is not uttered, even mentally, or not perceived or simultaneous with any perception.
 
3. date analysis:

 “X is present” uttered at time t means “X occurs at t”; etc.
Problem for (1-3): the analysandum and the analysans don't convey the same information; hence, they don't mean the same.  “I'm in pain now” doesn't convey the same info as “I'm in pain at 2 o'clock” even if now it is 2 o'clock. To go from one to the other, one has to know the date of “now”.  Note, again, the analogy to looking at a map without knowing where you are in the map (i.e., where the 'here' is on the map)
 

The new tenseless theory frankly admits that tensed statements are not translatable into tenseless statements. However, it holds that the truth conditions of tensed statements (the facts that make them true or false) are expressible in tenseless statements, without any need to appeal to A (tensed) facts.  In other words, tensed statements or propositions are made true or false by tenseless facts.
The basic version of the method is given by Mellor:

Any tensed sentence or proposition A temporally relates a certain event e to the present by saying two things:

1. whether e is earlier or later than the present
2. what the temporal distance d between e and the present is.

NOTE: actually, (2) is not necessary: consider "the war ended."

Here are the tenseless truth conditions:  A is true at time t (where t is a date) iff

1. e is earlier or later than t just as e is with respect to the present.
2. the distance d' between e and t is equal to d. 

For example, "yesterday it rained" is true on 2/3, 1763 iff on  2/2, 1763 it rained.
 

• Temporal indexical terms are rigid designators denoting times. So, “now” uttered at time t is a rigid designator for t and has no sense attached to it (it works like a proper noun).

NOTE: an indexical term or phrase is one whose reference can be known only by knowing the when or where of its use or its user; for example, "I" "you" "here" "now' are indexicals
Problem: one might object that “now” has a sense, namely ‘presentness.’ (Smith)
 
• “Joe runs now” (S) uttered at t and “Joe runs at t” (V) have different senses (they don't mean the same). However, they report the same fact, namely the tenseless fact expressed by V.  Hence, A-statements co-report the same facts as B-statements.

Objection: why not say that V reports the same fact as S (a tensed fact)?
Objection: “1980 is now,” although true in 1980, must have different truth conditions from “1980 is in 1980”, because the latter is metaphysically true, but the former is contingently true.
Reply: the former is contingently true because in some worlds it's not uttered in 1980; however, in the world at which it is, it co-reports with “1980 is in 1980.”
 

C. The dialectical method.

While the previous two methods of investigation are essentially based on considerations about the language of time, the dialectical method follows a more traditional path.  It tries to reject a  view of time by considering its implications and showing them to be unacceptable.  Here first we consider criticisms of the tensed view of time coming from detensers (as people who believe there is no tense are called), and then criticisms of the tenseless view of time by tense theorists.

1. Detenser's criticisms of the tensed view.

• In the tensed view of time, the 'now' flows along the series S of events.  An event E, for example, acquires and loses presentness.  This, in the tensed view, is the essence of change.  However, the event E acquiring presentness is itself an event.  Yet, it cannot be an event in the series S. Hence, it must be an event in some other series.  This involves introducing a meta-time, or giving up explaining change (Broad).

 
• How fast does the 'now' flow?  The natural answer is something like "at one second per second".  Detensers find this answer unacceptable on two grounds:
1. A movement involves two series whose items are correlated (e.g., the positions of a car and those of moments of time).  So, the positions of the 'now' must correlate to moments of time in some meta-time.  Hence, one ends up with two time series.
2. The answer 'at one second per second' is tautologous, amounting to saying that there is one second in every second.  This says nothing about the speed of the movement (compare: the car moves at one meter per meter)

Replies:
• No need to appeal to a meta-time.  One could just say that time flows at the rate of one second for every n meters covered by the car.
• Since the flow of time is that to which other things are compared to, asking how fast time flows is similar to asking how long the standard meter is Paris is long, a meaningless question (standards don't admit of self-predication)
 
• McTaggart’s argument against the reality of the A series (i.e., of tense)

2. Tenser’s criticism of tenseless view.
 
The B series is static (relations of “earlier” and “later” are permanent), and hence there is no change in it.  Each event (e.g. death of Queen Anne) has a  fixed position, and does not begin or cease to be because there is no “now”  (McTaggart)
Reply: it is true that the B-series as a whole does not change and that neither events nor facts change.  However, things in it do change because they have different properties at different dates; e.g., the poker being hot at t1 and cold at t2 (Russell).
Duplication: Merely having different properties at different dates doesn't constitute change: the property of “being hot at t1”  and “cold at t2” belong to the poker at every date.  The situation is analogous to the poker being hot at one end and cold at the other, which constitutes no change in the poker.  
 
 

D. The phenomenological method.

This is a strategy adopted by tensers.  The idea behind it is that any adequate account of time must accord with our basic experience of the world.  The claim is that the tenseless view unable to account for fundamental ways in which we look at time, namely our different attitudes towards past, present and future, our capacity to act timely, and our impression that time does actually pass or flow:
 

1. Our different attitudes towards past, present and future. When the dentist session (C) is over at time t, I say “That's over!” (O), and rejoice.  However, I am not thanking goodness for what B-theorists think makes O true at t, namely that C is earlier than t.  For, that C is earlier than t is a fact also before and during the root canal. Rather, I'm thanking goodness for the fact that the drilling stopped, i.e. was present and now is past (a tensed fact). (Prior).

Reply:  The reason I'm relieved is that I believe that it's over (if it were over but I didn't know it, I would not be relieved).  My being relieved is justified only if my belief is true.  But the truth conditions of a tensed belief are tenseless.  So, at the end I'm justifiably relieved at t because C is earlier than t or, which is the same, O is true.  It's just an empirical fact that usually (masochists apart) we are glad after the pain stopped.
 
2. Since we act on the basis of our beliefs, we need tenses in order to act timely.  For, suppose I want to hear the 1 o'clock news; then, I'll turn on the radio at 1 o'clock.  But in order to do that, something must happen in my set of beliefs at 1 o'clock (or its whereabouts), i.e. some sentence I entertain (e.g. "it's 1 o'clock now") must become true at 1 o'clock.  But tenseless sentences don't change their truth value.  Hence, we need tensed sentences, which can change their truth value only if there are tensed facts.

Reply: It's true that only tensed sentences change truth value and that for this reason they are needed for action.  However, the existence of tensed facts is not  necessary to account for the property of changing truth value that tensed sentences have.
 
3. Many have the definite impression of perceiving the flow of time.

Reply: We don't perceive the flow ot time.  It is the succession of different attitudes and perceptions (anticipation and dread, perception and pain, memory and relief) that gives rise to the impression of the flow of time.

This is an approach adopted by detensers. The idea here is to show that the tensed view of time is incompatible with a well established theory, namely Special Relativity.  We shall not go into this; however, it's fair to point out that whether the tensed view is incompatible with Special Relativity is a matter of controversy (for example, Smith has argued that it is not).