The original Daniel Roth Instantaneous Perpetual was launched in 1998, and based on a Lemania ebauche.

Semi-instantaneous Perpetual ref. 117; circa 1998. Fitted with a Lemania 8810 base movement and n perpetual calendar module designed in cooperation with Philippe Dufour himself. See the addendum at the bottom of the article for more on the semi-instantaneou nature of this first model.

Above version, ref. 117i.L40.888, has the same Lemania base but is presented with a skeleton dial. This version was made exclusively for the Asian market, according to The HourGlass, the long time distributer of Daniel Roth in Asia.

In 2003, the perpetual calendar module was modified for better performance and reintroduced, this time with a Girard Perregaux cal. 3000 base movement.

 
The revamped Instantaneous Perpetual of 2003. The perpetual calendar module was modified for better functioning, and the base movement was changed to the reliable Girard Perregaux cal. 3000; it was then renamed ref. 119.

The GP base movement in Daniel Roth high complications is extremely well finished, more so than most other iterations of the same movement.  

A look at the evolution of the Instantaneous Perpetual provides a glimpse into the evolution of Daniel Roth watches over the years, from the rather staid original to the current version. The 1998 original and the 2006 version look very different when compared to each other, but when you consider the history of instantaneous perpetual as a whole, it is easy to see where the 2006 came from; the design team at Daniel Roth have evidently managed to keep the spirit of the original watch and preserving its key aesthetic elements.

Despite the numerous changes the Instantaneous Perpetual has undergone, it still remains an underapprciated and remarkable horological tour de force. Apart fom a few, early Vianney Halter Antiqua watches, I do not believe there is another instantaneous perpetual calendar only complicated wristwatch in current production.

An instantaneous perpetual calendar is complex because it has to be constructed and tuned just right, so that all of the calendar functions change instantaneously at midnight. That is difficult because of the trememdous force required at one instant in time, as opposed to the gradual and progressive release of force in a regular perpetual calendar. In an instantaneous perpetual, the force required is slowly built up, before being released at midnight, when a finger-piece actuates a lever that changes all the indications of the calendar.

Beautifully finished dial side of the base plate, visible through skeleton dial.

One practical advantage of the instantaneous perpetual is the ability to set the time at any time, except at precisely midnight, something lacking in most other perpetual calendars. In a progressively changing perpetual, usually there is a window between 9 and 3, or thereabouts, where setting the time will break the mechanism. Not so with the instantaneous perpetual, since all functions change at one moment only.

Being one of the few that manages to manufacture such a watch, the Instantaneous Perpetual is a Daniel Roth trademark complication, as much as the tourbillon. Daniel Roth only manages to make about 20 of these per year by the way. What is even more interesting is that Daniel Roth makes the instantaneous perpetual calendar plates for Girard Perregaux, itself a movement manufacture, which then uses them inside the Vintage 1945 instantaneous perpetual calendar.

Instantaneous Perpetual in white gold

The instantaneous perpetual is one of my favourite models, I like the multi-layer skeleton dial and the depth it conveys, as well as the details of the perpetual calendar plate visible through the dial. The guilloche base plate works especially well, without the skeleton dial it would probably look too ostentatious, but in this case, when partially obscured by the dial, it results in a wonderful aesthetic.

- SJX

Addendum: Only the models with hands, as opposed to discs in windows, indicating the day and month are truly instantaneous. In other words, in those models, the hands all jump at midnight. The model with the discs, ref. 117 shown in the first picture at the top of the page, is semi-instantaneous as the weight of the discs do not allow for an instantaneous jump. Many thanks to Gerald Roden for this tidbit of information.