There appear to be two issues here:
1. Whether imposition of ashes must occur only during the Mass
2. Whether the imposition can be postponed to any other day
I think the answers are available at these Catholic sites:
The rite for the blessing and imposition of ashes on Ash Wednesday follows the homily at Mass.
This service is for Ash Wednesday. Where, because of particular circumstances, Ash Wednesday cannot be celebrated, this service may be used on/up to the First Sunday in Lent.
About the postponement of the All Souls Day blessing of graves, I suggest that you consut a liturgist.
Glad to be at your service, Michael
February,18th 2015 was Ash Wednesday.
In St.Michaels Church no ashes were imposed during the 7 and 8 am masses.Announcements were made that ashes would be imposed only after the 7.30 am and 8.30 nouvena got over which meant that parishioners who did not want to hear the nouvena were being forced to do so if they wanted ashes.
Throughout Mumbai, however ashes came to be imposed only during the mass.
A couple years ago All Souls Day came on a Wednesday on that day also the blessing of the graves was postponed to Thursday.The late Fr.Salvadore Rodrigues sent me a defamatory notice through a solicitor for having spoken about this. However he did not to file a case against me despite me telling one of the Church Advocates to please tell him to file the case against me as I would be given an opportunity to expose the truth.
My question is if one considers the imposition of Ashes and Blessing of graves as symbolic and having no religious value.
Please let me know your views as and when you get time.